diff --git a/lib/EioDescriptor.php b/lib/EioDescriptor.php
new file mode 100644
index 0000000..4d124e6
--- /dev/null
+++ b/lib/EioDescriptor.php
@@ -0,0 +1,154 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\Reactor;
+use Amp\Promise;
+use Amp\Deferred;
+
+class EioDescriptor implements Descriptor {
+    private $reactor;
+    private $fh;
+    private $increment;
+    private $decrement;
+    private $isCloseInitialized = false;
+
+    /**
+     * @param \Amp\Reactor $reactor
+     * @param resource $fh An eio file handle
+     * @param callable $inc
+     * @param callable $dec
+     */
+    public function __construct(Reactor $reactor, $fh, callable $inc, callable $dec) {
+        $this->reactor = $reactor;
+        $this->fh = $fh;
+        $this->increment = $inc;
+        $this->decrement = $dec;
+    }
+
+    public function __destruct() {
+        if (empty($this->isCloseInitialized)) {
+            $this->close();
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function read($offset, $len) {
+        \call_user_func($this->increment);
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_read($this->fh, $offset, $len, $priority, [$this, "onRead"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onRead($promisor, $result, $req) {
+        \call_user_func($this->decrement);
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed($result);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function write($offset, $data) {
+        \call_user_func($this->increment);
+        $promisor = new Deferred;
+        $length = 0;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_write($this->fh, $data, $length, $offset, $priority, [$this, "onWrite"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onWrite($promisor, $result, $req) {
+        \call_user_func($this->decrement);
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed($result);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function truncate($length = 0) {
+        \call_user_func($this->increment);
+        $promisor = new Deferred;
+        $length = 0;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_truncate($this->fh, $length, $priority, [$this, "onTruncate"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onTruncate($promisor, $result, $req) {
+        \call_user_func($this->decrement);
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed();
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function stat() {
+        \call_user_func($this->increment);
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_fstat($this->fh, $priority, [$this, "onStat"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onStat($promisor, $result, $req) {
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $stat["isdir"] = (bool) ($stat["mode"] & Filesystem::S_IFDIR);
+            $stat["isfile"] = (bool) ($stat["mode"] & Filesystem::S_IFREG);
+        }
+        \call_user_func($this->decrement);
+        $promisor->succeed($result);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function close() {
+        $this->isCloseInitialized = true;
+        \call_user_func($this->increment);
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_close($this->fh, $priority, [$this, "onClose"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onClose($promisor, $result, $req) {
+        \call_user_func($this->decrement);
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed();
+        }
+    }
+}
diff --git a/lib/EioFilesystem.php b/lib/EioFilesystem.php
new file mode 100644
index 0000000..bfb0ca2
--- /dev/null
+++ b/lib/EioFilesystem.php
@@ -0,0 +1,368 @@
+<?php
+
+namespace Amp\Fs;
+
+use Amp\Reactor;
+use Amp\Promise;
+use Amp\Success;
+use Amp\Failure;
+use Amp\Deferred;
+
+class EioFilesystem implements Filesystem {
+    const S_IFDIR = 0x4000;
+    const S_IFREG = 0x8000;
+
+    private $reactor;
+    private $stream;
+    private $watcher;
+    private $callableDelReq;
+    private $internalIncrement;
+    private $internalDecrement;
+    private $pending = 0;
+
+    public function __construct(Reactor $reactor = null) {
+        \eio_init();
+        $this->reactor = $reactor ?: \Amp\reactor();
+        $this->stream = \eio_get_event_stream();
+        $this->callableDelReq = function() {
+            $this->decrementPending();
+        };
+        $this->internalIncrement = function() {
+            $this->incrementPending();
+        };
+        $this->internalDecrement = function() {
+            $this->decrementPending();
+        };
+        $this->watcher = $this->reactor->onReadable($this->stream, function() {
+            while (\eio_npending()) {
+                \eio_poll();
+            }
+        }, $options = ["enable" => false]);
+    }
+
+    private function incrementPending() {
+        if ($this->pending++ === 0) {
+            $this->reactor->enable($this->watcher);
+        }
+    }
+
+    private function decrementPending() {
+        if ($this->pending-- === 1) {
+            $this->reactor->disable($this->watcher);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function open($path, $mode = self::READ) {
+        $flags = 0;
+
+        if (($mode & self::READ) && ($mode & self::WRITE)) {
+            $flags = \EIO_O_RDWR | \EIO_O_CREAT;
+        } elseif ($mode & self::READ) {
+            $flags = \EIO_O_RDONLY;
+        } elseif ($mode & self::WRITE) {
+            $flags = \EIO_O_WRONLY | \EIO_O_CREAT;
+        } else {
+            return new Failure(new \InvalidArgumentException(
+                "Invalid file open mode: Filesystem::READ or Filesystem::WRITE or both required"
+            ));
+        }
+
+        $mode = \EIO_S_IRUSR | \EIO_S_IWUSR | \EIO_S_IXUSR;
+        $priority = \EIO_PRI_DEFAULT;
+
+        $this->incrementPending();
+        $promisor = new Deferred;
+        \eio_open($path, $flags, $mode, $priority, [$this, "onOpen"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onOpen($promisor, $result, $req) {
+        $this->decrementPending();
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $descriptor = new EioDescriptor(
+                $this->reactor,
+                $result,
+                $this->internalIncrement,
+                $this->internalDecrement
+            );
+            $promisor->succeed($descriptor);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function stat($path) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_stat($path, $priority, [$this, "onStat"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onStat($promisor, $result, $req) {
+        if ($result === -1) {
+            $stat = null;
+        } else {
+            $stat = $result;
+            $stat["isdir"] = (bool) ($stat["mode"] & self::S_IFDIR);
+            $stat["isfile"] = (bool) ($stat["mode"] & self::S_IFREG);
+        }
+        $this->decrementPending();
+        $promisor->succeed($stat);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function lstat($path) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_lstat($path, $priority, [$this, "onStat"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function symlink($target, $link) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_symlink($target, $link, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onGenericResult($promisor, $result, $req) {
+        $this->decrementPending();
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed(true);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rename($from, $to) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_rename($from, $to, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function unlink($path) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_unlink($path, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function mkdir($path, $mode = 0644) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_mkdir($path, $mode, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function rmdir($path) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_rmdir($path, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function scandir($path) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $flags = \EIO_READDIR_STAT_ORDER | \EIO_READDIR_DIRS_FIRST;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_readdir($path, $flags, $priority, [$this, "onScandir"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onScandir($promisor, $result, $req) {
+        $this->decrementPending();
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed($result["names"]);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function chmod($path, $mode) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_chmod($path, $mode, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function chown($path, $uid, $gid) {
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_chown($path, $uid, $gid, $priority, [$this, "onGenericResult"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function get($path) {
+        $flags = $flags = \EIO_O_RDONLY;
+        $mode = 0;
+        $priority = \EIO_PRI_DEFAULT;
+
+        $this->incrementPending();
+        $promisor = new Deferred;
+        \eio_open($path, $flags, $mode, $priority, [$this, "onGetOpen"], $promisor);
+
+        return $promisor->promise();
+    }
+
+    private function onGetOpen($promisor, $result, $req) {
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $priority = \EIO_PRI_DEFAULT;
+            \eio_fstat($result, $priority, [$this, "onGetFstat"], [$result, $promisor]);
+        }
+    }
+
+    private function onGetFstat($fhAndPromisor, $result, $req) {
+        list($fh, $promisor) = $fhAndPromisor;
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+            return;
+        }
+
+        $offset = 0;
+        $length = $result["size"];
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_read($fh, $length, $offset, $priority, [$this, "onGetRead"], $fhAndPromisor);
+    }
+
+    private function onGetRead($fhAndPromisor, $result, $req) {
+        list($fh, $promisor) = $fhAndPromisor;
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_close($fh, $priority, $this->callableDelReq);
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed($result);
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function put($path, $contents) {
+        $flags = \EIO_O_RDWR | \EIO_O_CREAT;
+        $mode = \EIO_S_IRUSR | \EIO_S_IWUSR | \EIO_S_IXUSR;
+        $priority = \EIO_PRI_DEFAULT;
+
+        $this->incrementPending();
+        $promisor = new Deferred;
+        $data = [$contents, $promisor];
+        \eio_open($path, $flags, $mode, $priority, [$this, "onPutOpen"], $data);
+
+        return $promisor->promise();
+    }
+
+    private function onPutOpen($data, $result, $req) {
+        list($contents, $promisor) = $data;
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $length = strlen($contents);
+            $offset = 0;
+            $priority = \EIO_PRI_DEFAULT;
+            $callback = [$this, "onPutWrite"];
+            $fhAndPromisor = [$result, $promisor];
+            \eio_write($result, $contents, $length, $offset, $priority, $callback, $fhAndPromisor);
+        }
+    }
+
+    private function onPutWrite($fhAndPromisor, $result, $req) {
+        list($fh, $promisor) = $fhAndPromisor;
+        \eio_close($fh);
+        $priority = \EIO_PRI_DEFAULT;
+        \eio_close($fh, $priority, $this->callableDelReq);
+        if ($result === -1) {
+            $promisor->fail(new \RuntimeException(
+                \eio_get_last_error($req)
+            ));
+        } else {
+            $promisor->succeed($result);
+        }
+    }
+
+    public function __destruct() {
+        $this->stream = null;
+        $this->reactor->cancel($this->watcher);
+
+        /**
+         * pecl/eio has a race condition issue when freeing threaded
+         * resources and we can get intermittent segfaults at script
+         * shutdown in certain cases if we don't wait for a moment.
+         *
+         * @TODO see if we can PR a fix for this problem in pecl/eio
+         */
+        usleep(1000);
+    }
+}
diff --git a/lib/functions.php b/lib/functions.php
index d74be2d..f1a1c60 100644
--- a/lib/functions.php
+++ b/lib/functions.php
@@ -16,12 +16,8 @@ function fs(Filesystem $assign = null) {
         return $filesystem;
     } elseif (\extension_loaded("uv")) {
         return ($filesystem = new UvFilesystem(\Amp\reactor()));
-    /*
-    // @TODO
-    } elseif (\extension_loaded("eio") {
-        return ($filesystem = new EioFilesystem);
-    }
-    */
+    } elseif (\extension_loaded("eio")) {
+        return ($filesystem = new EioFilesystem(\Amp\reactor()));
     } else {
         return ($filesystem = new BlockingFilesystem(\Amp\reactor()));
     }
diff --git a/test/EioFilesystemTest.php b/test/EioFilesystemTest.php
new file mode 100644
index 0000000..6222a93
--- /dev/null
+++ b/test/EioFilesystemTest.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Amp\Fs\Test;
+
+use Amp\Reactor;
+use Amp\NativeReactor;
+use Amp\Fs\EioFilesystem;
+
+class EioFilesystemTest extends FilesystemTest {
+    protected function getReactor() {
+        if (extension_loaded("eio")) {
+            return new NativeReactor;
+        } else {
+            $this->markTestSkipped(
+                "php-uv extension not loaded"
+            );
+        }
+    }
+
+    protected function getFilesystem(Reactor $reactor) {
+        return new EioFilesystem($reactor);
+    }
+}
diff --git a/test/FilesystemTest.php b/test/FilesystemTest.php
index d324065..8a4e25b 100644
--- a/test/FilesystemTest.php
+++ b/test/FilesystemTest.php
@@ -104,7 +104,7 @@ abstract class FilesystemTest extends \PHPUnit_Framework_TestCase {
 
             $toUnlink = __DIR__ . "/fixture/unlink";
 
-            yield $fs->put($toUnlink, "");
+            yield $fs->put($toUnlink, "unlink me");
             $this->assertTrue((bool) (yield $fs->stat($toUnlink)));
             yield $fs->unlink($toUnlink);
             $this->assertNull(yield $fs->stat($toUnlink));
@@ -125,5 +125,4 @@ abstract class FilesystemTest extends \PHPUnit_Framework_TestCase {
             $this->assertNull(yield $fs->stat($dir));
         });
     }
-
 }