diff --git a/examples/worker-process.php b/examples/worker-process.php
new file mode 100755
index 0000000..5d73627
--- /dev/null
+++ b/examples/worker-process.php
@@ -0,0 +1,22 @@
+#!/usr/bin/env php
+<?php
+require dirname(__DIR__).'/vendor/autoload.php';
+
+use Icicle\Concurrent\Worker\HelloTask;
+use Icicle\Concurrent\Worker\WorkerProcess;
+use Icicle\Coroutine;
+use Icicle\Loop;
+
+Coroutine\create(function () {
+    $worker = new WorkerProcess();
+    $worker->start();
+
+    $returnValue = (yield $worker->enqueue(new HelloTask()));
+
+    printf("Return value: %d\n", $returnValue);
+
+    $code = (yield $worker->shutdown());
+    printf("Code: %d\n", $code);
+})->done();
+
+Loop\run();
diff --git a/examples/worker-thread.php b/examples/worker-thread.php
index 8641c8b..68335cf 100755
--- a/examples/worker-thread.php
+++ b/examples/worker-thread.php
@@ -2,26 +2,17 @@
 <?php
 require dirname(__DIR__).'/vendor/autoload.php';
 
-use Icicle\Concurrent\Worker\TaskInterface;
+use Icicle\Concurrent\Worker\HelloTask;
 use Icicle\Concurrent\Worker\WorkerThread;
 use Icicle\Coroutine;
 use Icicle\Loop;
 
-class HelloTask implements TaskInterface
-{
-    public function run()
-    {
-        echo "Hello!\n";
-        return 42;
-    }
-}
-
 Coroutine\create(function () {
     $worker = new WorkerThread();
     $worker->start();
 
     $returnValue = (yield $worker->enqueue(new HelloTask()));
     yield $worker->shutdown();
-});
+})->done();
 
 Loop\run();
diff --git a/src/Process/Process.php b/src/Process/Process.php
new file mode 100644
index 0000000..457cf10
--- /dev/null
+++ b/src/Process/Process.php
@@ -0,0 +1,314 @@
+<?php
+namespace Icicle\Concurrent\Process;
+
+use Exception;
+use Icicle\Coroutine\Coroutine;
+use Icicle\Socket\Stream\ReadableStream;
+use Icicle\Socket\Stream\WritableStream;
+
+class Process
+{
+    /**
+     * @var resource|null
+     */
+    private $process;
+
+    /**
+     * @var string
+     */
+    private $command;
+
+    /**
+     * @var string
+     */
+    private $cwd = '';
+
+    /**
+     * @var array
+     */
+    private $env = [];
+
+    /**
+     * @var array
+     */
+    private $options;
+
+    /**
+     * @var resource|null
+     */
+    private $stdin;
+
+    /**
+     * @var resource|null
+     */
+    private $stdout;
+
+    /**
+     * @var resource|null
+     */
+    private $stderr;
+
+    /**
+     * @var int
+     */
+    private $pid = 0;
+
+    /**
+     * @var \Icicle\Promise\PromiseInterface
+     */
+    private $promise;
+
+    /**
+     * @param   string $command Command to run.
+     * @param   string|null $cwd Working directory or use null to use the working directory of the current PHP process.
+     * @param   mixed[] $env Environment variables or use null to inherit from the current PHP process.
+     * @param   mixed[] $options Options for proc_open().
+     */
+    public function __construct($command, $cwd = '', array $env = [], array $options = [])
+    {
+        $this->command = (string) $command;
+
+        if ('' !== $cwd) {
+            $this->cwd = (string) $cwd;
+        }
+
+        foreach ($env as $key => $value) {
+            if (!is_array($value)) { // $env cannot accept array values.
+                $this->env[(string) $key] = (string) $value;
+            }
+        }
+
+        $this->options = $options;
+    }
+
+    /**
+     * Stops the process if it is still running.
+     */
+    public function __destruct()
+    {
+        $this->kill(); // Will only terminate if the process is still running.
+    }
+
+    /**
+     * Resets process values.
+     */
+    public function __clone()
+    {
+        $this->process = null;
+        $this->promise = null;
+        $this->pid = 0;
+        $this->stdin = null;
+        $this->stdout = null;
+        $this->stderr = null;
+    }
+
+    /**
+     * @throws \Exception
+     */
+    public function start()
+    {
+        if (null !== $this->promise) {
+            throw new Exception('The process has already been started.');
+        }
+
+        $fd = [
+            ['pipe', 'r'], // stdin
+            ['pipe', 'w'], // stdout
+            ['pipe', 'a'], // stderr
+            ['pipe', 'w'], // exit code pipe
+        ];
+
+        $command = sprintf('(%s) 3>/dev/null; code=$?; echo $code >&3; exit $code', $this->command);
+
+        $this->process = proc_open($command, $fd, $pipes, $this->cwd ?: null, $this->env ?: null, $this->options);
+
+        if (!is_resource($this->process)) {
+            throw new Exception('Could not start process.');
+        }
+
+        $status = proc_get_status($this->process);
+
+        $this->pid = $status['pid'];
+
+        list($this->stdin, $this->stdout, $this->stderr, $stream) = $pipes;
+
+//        $this->stdin = new WritableStream($pipes[0]);
+//        $this->stdout = new ReadableStream($pipes[1]);
+//        $this->stderr = new ReadableStream($pipes[2]);
+
+        $stream = new ReadableStream($stream);
+
+        $this->promise = new Coroutine($stream->read());
+        $this->promise = $this->promise
+            ->then(function ($code) {
+                if ('' === $code) {
+                    throw new Exception('Process ended unexpectedly.');
+                }
+                return (int) $code;
+            })
+            ->cleanup(function () use ($stream) {
+                proc_close($this->process);
+                $this->process = null;
+                //$this->stdin->close();
+                $stream->close();
+            });
+    }
+
+    /**
+     * @return \Generator
+     *
+     * @throws \Exception
+     */
+    public function join()
+    {
+        if (null === $this->promise) {
+            throw new Exception('The process has not been started.');
+        }
+
+        try {
+            yield $this->promise;
+        } finally {
+            //$this->stdout->close();
+            //$this->stderr->close();
+        }
+    }
+
+    /**
+     */
+    public function kill()
+    {
+        if (is_resource($this->process)) {
+            proc_terminate($this->process, 9); // Sends SIGKILL.
+            $this->process = null;
+        }
+    }
+
+    /**
+     * Sends the given signal to the process.
+     *
+     * @param int $signo Signal number to send to process.
+     *
+     * @throws Exception
+     */
+    public function signal($signo)
+    {
+        if (!$this->isRunning()) {
+            throw new Exception('The process is not running.');
+        }
+
+        proc_terminate($this->process, (int) $signo);
+    }
+
+    /**
+     * Returns the PID of the child process. Value is only meaningful if the process has been started and PHP was not
+     * compiled with --enable-sigchild.
+     *
+     * @return int
+     */
+    public function getPid()
+    {
+        return $this->pid;
+    }
+
+    /**
+     * Returns the command to execute.
+     *
+     * @return  string The command to execute.
+     */
+    public function getCommand()
+    {
+        return $this->command;
+    }
+
+    /**
+     * Gets the current working directory.
+     *
+     * @return string The current working directory or null if inherited from the current PHP process.
+     */
+    public function getWorkingDirectory()
+    {
+        if ('' === $this->cwd) {
+            return getcwd() ?: '';
+        }
+
+        return $this->cwd;
+    }
+
+    /**
+     * Gets the environment variables array.
+     *
+     * @return mixed[] Array of environment variables.
+     */
+    public function getEnv()
+    {
+        return $this->env;
+    }
+
+    /**
+     * Gets the options to pass to proc_open().
+     *
+     * @return mixed[] Array of options.
+     */
+    public function getOptions()
+    {
+        return $this->options;
+    }
+
+    /**
+     * Determines if the process is still running.
+     *
+     * @return  bool
+     */
+    public function isRunning()
+    {
+        return is_resource($this->process);
+    }
+
+    /**
+     * Gets the process input stream (STDIN).
+     *
+     * @return  resource
+     *
+     * @throws  Exception If the process has not been started.
+     */
+    public function getStdIn()
+    {
+        if (null === $this->stdin) {
+            throw new Exception('The process has not been started.');
+        }
+
+        return $this->stdin;
+    }
+
+    /**
+     * Gets the process output stream (STDOUT).
+     *
+     * @return  resource
+     *
+     * @throws  Exception If the process has not been started.
+     */
+    public function getStdOut()
+    {
+        if (null === $this->stdout) {
+            throw new Exception('The process has not been started.');
+        }
+
+        return $this->stdout;
+    }
+
+    /**
+     * Gets the process error stream (STDERR).
+     *
+     * @return  resource
+     *
+     * @throws  Exception If the process has not been started.
+     */
+    public function getStdErr()
+    {
+        if (null === $this->stderr) {
+            throw new Exception('The process has not been started.');
+        }
+
+        return $this->stderr;
+    }
+}
\ No newline at end of file
diff --git a/src/Worker/HelloTask.php b/src/Worker/HelloTask.php
new file mode 100644
index 0000000..c1cd635
--- /dev/null
+++ b/src/Worker/HelloTask.php
@@ -0,0 +1,11 @@
+<?php
+namespace Icicle\Concurrent\Worker;
+
+class HelloTask implements TaskInterface
+{
+    public function run()
+    {
+        echo "Hello";
+        return 42;
+    }
+}
diff --git a/src/Worker/WorkerProcess.php b/src/Worker/WorkerProcess.php
new file mode 100644
index 0000000..719a025
--- /dev/null
+++ b/src/Worker/WorkerProcess.php
@@ -0,0 +1,90 @@
+<?php
+namespace Icicle\Concurrent\Worker;
+
+use Icicle\Concurrent\Exception\SynchronizationError;
+use Icicle\Concurrent\Process\Process;
+use Icicle\Concurrent\Sync\Channel;
+use Icicle\Concurrent\Sync\ChannelInterface;
+use Icicle\Coroutine\Coroutine;
+use Icicle\Socket\Stream\ReadableStream;
+
+class WorkerProcess implements WorkerInterface
+{
+    private $process;
+
+    private $channel;
+
+    public function __construct()
+    {
+        $this->process = new Process(sprintf('%s %s/process.php', PHP_BINARY, __DIR__), __DIR__);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isRunning()
+    {
+        return $this->process->isRunning();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function isIdle()
+    {
+        return false;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function start()
+    {
+        $this->process->start();
+
+        $this->channel = new Channel(
+            $this->process->getStdOut(),
+            $this->process->getStdIn()
+        );
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function kill()
+    {
+        $this->process->kill();
+    }
+
+    /**
+     * @return \Generator
+     */
+    public function join()
+    {
+        return $this->process->join();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function shutdown()
+    {
+        yield $this->channel->send(1);
+        yield $this->process->join();
+        //var_dump('SENT SHUTDOWN');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function enqueue(TaskInterface $task)
+    {
+        if (!$this->channel instanceof ChannelInterface) {
+            throw new SynchronizationError('Worker has not been started.');
+        }
+
+        yield $this->channel->send($task);
+
+        yield $this->channel->receive();
+    }
+}
\ No newline at end of file
diff --git a/src/Worker/process.php b/src/Worker/process.php
new file mode 100644
index 0000000..140d9e3
--- /dev/null
+++ b/src/Worker/process.php
@@ -0,0 +1,41 @@
+<?php
+namespace Icicle\Concurrent\Worker;
+
+require dirname(dirname(__DIR__)) . '/vendor/autoload.php';
+
+use Icicle\Concurrent\Sync\Channel;
+use Icicle\Concurrent\Sync\ChannelInterface;
+use Icicle\Coroutine\Coroutine;
+use Icicle\Loop;
+
+function run(ChannelInterface $channel)
+{
+    try {
+        while (true) {
+            $task = (yield $channel->receive());
+
+            // Shutdown request
+            if ($task === 1) {
+                break;
+            }
+
+            if (!($task instanceof TaskInterface)) {
+                throw new \Exception('Invalid message.');
+            }
+
+            yield $channel->send(yield $task->run());
+        }
+    } finally {
+        $channel->close();
+    }
+}
+
+ob_start(function ($data) {
+    $written = fwrite(STDERR, $data);
+    return '';
+}, 1);
+
+$coroutine = new Coroutine(run(new Channel(STDIN, STDOUT)));
+$coroutine->done();
+
+Loop\run();