Index: tests/t3lib/t3lib_extmgm_testcase.php
===================================================================
--- tests/t3lib/t3lib_extmgm_testcase.php	(Revision 7196)
+++ tests/t3lib/t3lib_extmgm_testcase.php	(Arbeitskopie)
@@ -401,5 +401,66 @@
 			'newA, newB, fieldX', $GLOBALS['TCA'][$table]['palettes']['generatedFor-fieldA']['showitem']
 		);
 	}
+
+
+	/////////////////////////////////////////
+	// Tests concerning getExtensionVersion
+	/////////////////////////////////////////
+
+	/**
+	 * Data provider for negative getExtensionVersion() tests.
+	 *
+	 * @return array
+	 */
+	public function getExtensionVersionFaultyDataProvider() {
+		return array(
+			array(''),
+			array(0),
+			array(new stdClass()),
+			array(TRUE),
+		);
+	}
+
+	/**
+	 * @test
+	 * @expectedException InvalidArgumentException
+	 * @dataProvider getExtensionVersionFaultyDataProvider
+	 */
+	public function getExtensionVersionForFaultyExtensionKeyThrowsException($key) {
+		t3lib_extMgm::getExtensionVersion($key);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getExtensionVersionForNotLoadedExtensionReturnsEmptyString() {
+		t3lib_extMgm::clearExtensionKeyMap();
+
+		$uniqueSuffix = uniqid('test');
+		$extensionKey = 'unloadedextension' . $uniqueSuffix;
+
+		$this->assertEquals(
+			'',
+			t3lib_extMgm::getExtensionVersion($extensionKey)
+		);
+	}
+
+	/**
+	 * @test
+	 */
+	public function getExtensionVersionForLoadedExtensionReturnsExtensionVersion() {
+		t3lib_extMgm::clearExtensionKeyMap();
+
+		$uniqueSuffix = uniqid('test');
+		$extensionKey = 'unloadedextension' . $uniqueSuffix;
+
+		$GLOBALS['TYPO3_LOADED_EXT'][$extensionKey] = array(
+			'siteRelPath' => 'typo3_src/tests/t3lib/fixtures/',
+		);
+		$this->assertEquals(
+			'1.2.3',
+			t3lib_extMgm::getExtensionVersion($extensionKey)
+		);
+	}
 }
 ?>
\ No newline at end of file
Index: tests/t3lib/fixtures/ext_emconf.php
===================================================================
--- tests/t3lib/fixtures/ext_emconf.php	(Revision 0)
+++ tests/t3lib/fixtures/ext_emconf.php	(Revision 0)
@@ -0,0 +1,37 @@
+<?php
+$EM_CONF[$_EXTKEY] = array(
+	'title' => '',
+	'description' => 'This is a fixture extension configuration file used for unit tests.',
+	'category' => '',
+	'shy' => 1,
+	'dependencies' => '',
+	'conflicts' => '',
+	'priority' => '',
+	'loadOrder' => '',
+	'module' => '',
+	'state' => 'stable',
+	'internal' => 1,
+	'uploadfolder' => 0,
+	'createDirs' => '',
+	'modify_tables' => '',
+	'clearCacheOnLoad' => 0,
+	'lockType' => '',
+	'author' => '',
+	'author_email' => '',
+	'author_company' => '',
+	'CGLcompliance' => '',
+	'CGLcompliance_note' => '',
+	'version' => '1.2.3',
+	'_md5_values_when_last_written' => '',
+	'constraints' => array(
+		'depends' => array(
+		),
+		'conflicts' => array(
+		),
+		'suggests' => array(
+		),
+	),
+	'suggests' => array(
+	),
+);
+?>
\ No newline at end of file
Index: t3lib/class.t3lib_extmgm.php
===================================================================
--- t3lib/class.t3lib_extmgm.php	(Revision 7196)
+++ t3lib/class.t3lib_extmgm.php	(Arbeitskopie)
@@ -229,8 +229,27 @@
 		self::$extensionKeyMap = NULL;
 	}
 
+	/**
+	 * Retrieves the version of an installed extension.
+	 * If the extension is not installed, this function returns an empty string.
+	 *
+	 * @param string $key the key of the extension to look up, must not be empty
+	 * @return string the extension version as a string in the format "x.y.z",
+	 *                will be an empty string if the extension is not loaded
+	 */
+	public static function getExtensionVersion($key) {
+		if (!is_string($key) || empty($key)) {
+			throw new InvalidArgumentException('Extension key must be a non-empty string.');
+		}
+		if (!self::isLoaded($key)) {
+			return '';
+		}
 
+		$_EXTKEY = $key;
+		include(t3lib_extMgm::extPath($key) . 'ext_emconf.php');
 
+		return $EM_CONF[$key]['version'];
+	}