diff --git a/src/Composer/Command/DebugPackagesCommand.php b/src/Composer/Command/DebugPackagesCommand.php
index b92d06373..a953baed6 100644
--- a/src/Composer/Command/DebugPackagesCommand.php
+++ b/src/Composer/Command/DebugPackagesCommand.php
@@ -33,7 +33,7 @@ class DebugPackagesCommand extends Command
             ->setName('debug:packages')
             ->setDescription('Lists all existing packages and their version')
             ->setHelp(<<<EOT
-<info>php composer debug:packages</info>
+<info>php composer.phar debug:packages</info>
 
 EOT
             )
diff --git a/src/Composer/Command/InstallCommand.php b/src/Composer/Command/InstallCommand.php
index f5c8e9cca..55cb2d8e1 100644
--- a/src/Composer/Command/InstallCommand.php
+++ b/src/Composer/Command/InstallCommand.php
@@ -43,7 +43,7 @@ The <info>install</info> command reads the composer.json file from the
 current directory, processes it, and downloads and installs all the
 libraries and dependencies outlined in that file.
 
-<info>php composer install</info>
+<info>php composer.phar install</info>
 
 EOT
             )
@@ -51,10 +51,15 @@ EOT
     }
 
     protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        return $this->install($output, $input->getOption('dev'));
+    }
+
+    public function install(OutputInterface $output, $preferSource, $update = false)
     {
         $composer = $this->getComposer();
 
-        if ($input->getOption('dev')) {
+        if ($preferSource) {
             $composer->getDownloadManager()->setPreferSource(true);
         }
 
@@ -72,7 +77,30 @@ EOT
 
         // creating requirements request
         $request = new Request($pool);
-        if ($composer->getLocker()->isLocked()) {
+        if ($update) {
+            $output->writeln('> Updating dependencies.');
+            $listedPackages = array();
+            $installedPackages = $installedRepo->getPackages();
+
+            foreach ($composer->getPackage()->getRequires() as $link) {
+                $listedPackages[] = $link->getTarget();
+
+                foreach ($installedPackages as $package) {
+                    if ($package->getName() === $link->getTarget()) {
+                        $request->update($link->getTarget(), $link->getConstraint());
+                        continue 2;
+                    }
+                }
+
+                $request->install($link->getTarget(), $link->getConstraint());
+            }
+
+            foreach ($localRepo->getPackages() as $package) {
+                if (!in_array($package->getName(), $listedPackages)) {
+                    $request->remove($package->getName());
+                }
+            }
+        } elseif ($composer->getLocker()->isLocked()) {
             $output->writeln('> Found lockfile. Reading.');
 
             foreach ($composer->getLocker()->getLockedPackages() as $package) {
@@ -80,6 +108,7 @@ EOT
                 $request->install($package->getName(), $constraint);
             }
         } else {
+            $output->writeln('> Installing dependencies.');
             foreach ($composer->getPackage()->getRequires() as $link) {
                 $request->install($link->getTarget(), $link->getConstraint());
             }
@@ -116,7 +145,7 @@ EOT
             $installationManager->execute($operation);
         }
 
-        if (!$composer->getLocker()->isLocked()) {
+        if ($update || !$composer->getLocker()->isLocked()) {
             $composer->getLocker()->lockPackages($localRepo->getPackages());
             $output->writeln('> Locked');
         }
diff --git a/src/Composer/Command/UpdateCommand.php b/src/Composer/Command/UpdateCommand.php
new file mode 100644
index 000000000..90573a872
--- /dev/null
+++ b/src/Composer/Command/UpdateCommand.php
@@ -0,0 +1,58 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Command;
+
+use Composer\Autoload\AutoloadGenerator;
+use Composer\DependencyResolver;
+use Composer\DependencyResolver\Pool;
+use Composer\DependencyResolver\Request;
+use Composer\DependencyResolver\Operation;
+use Composer\Package\LinkConstraint\VersionConstraint;
+use Composer\Repository\PlatformRepository;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+/**
+ * @author Jordi Boggiano <j.boggiano@seld.be>
+ */
+class UpdateCommand extends Command
+{
+    protected function configure()
+    {
+        $this
+            ->setName('update')
+            ->setDescription('Updates your dependencies to the latest version, and updates the composer.lock file.')
+            ->setDefinition(array(
+                new InputOption('dev', null, InputOption::VALUE_NONE, 'Forces installation from package sources when possible, including VCS information.'),
+            ))
+            ->setHelp(<<<EOT
+The <info>update</info> command reads the composer.json file from the
+current directory, processes it, and updates, removes or installs all the
+dependencies.
+
+<info>php composer.phar update</info>
+
+EOT
+            )
+        ;
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output)
+    {
+        $composer = $this->getComposer();
+
+        $installCommand = $this->getApplication()->find('install');
+        return $installCommand->install($output, $input->getOption('dev'), true);
+    }
+}
diff --git a/src/Composer/Console/Application.php b/src/Composer/Console/Application.php
index 1f0f12e8a..b34607eee 100644
--- a/src/Composer/Console/Application.php
+++ b/src/Composer/Console/Application.php
@@ -64,6 +64,7 @@ class Application extends BaseApplication
     protected function registerCommands()
     {
         $this->add(new Command\InstallCommand());
+        $this->add(new Command\UpdateCommand());
         $this->add(new Command\DebugPackagesCommand());
     }
 }