diff --git a/css/youtube.css b/css/youtube.css
new file mode 100644
index 0000000..0bb8230
--- /dev/null
+++ b/css/youtube.css
@@ -0,0 +1,21 @@
+/**
+ * @file
+ *   CSS for the YouTube Field module.
+ */
+
+/* Takes effect when a field's 'size' display setting is 'responsive'. */
+.youtube-container--responsive {
+  overflow: hidden;
+  position: relative;
+  padding-bottom: 56.25%;
+  height: 0;
+}
+
+.youtube-container--responsive iframe {
+  border: none;
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+}
diff --git a/youtube.inc b/youtube.inc
index 2096287..09d90ab 100644
--- a/youtube.inc
+++ b/youtube.inc
@@ -14,6 +14,7 @@ function youtube_size_options() {
     '480x360' => '480px by 360px',
     '640x480' => '640px by 480px',
     '960x720' => '960px by 720px',
+    'responsive' => 'responsive (full-width)',
     'custom' => 'custom',
   );
 }
@@ -23,7 +24,11 @@ function youtube_size_options() {
  */
 function youtube_get_dimensions($size = NULL, $width = NULL, $height = NULL) {
   $dimensions = array();
-  if ($size == 'custom') {
+  if ($size == 'responsive') {
+    $dimensions['width'] = '100%';
+    $dimensions['height'] = '100%';
+  }
+  elseif ($size == 'custom') {
     $dimensions['width'] = (int) $width;
     $dimensions['height'] = (int) $height;
   }
diff --git a/youtube.info b/youtube.info
index 1767931..d0b556d 100644
--- a/youtube.info
+++ b/youtube.info
@@ -5,6 +5,7 @@ core = 7.x
 dependencies[] = field 
 dependencies[] = image
 dependencies[] = file
+stylesheets[all][] = css/youtube.css
 ; Information added by drupal.org packaging script on 2012-09-14
 version = "7.x-1.0"
 core = "7.x"
diff --git a/youtube.theme.inc b/youtube.theme.inc
index 48da8a7..d08bad3 100644
--- a/youtube.theme.inc
+++ b/youtube.theme.inc
@@ -45,6 +45,10 @@ function theme_youtube_video($variables) {
     height="' . $dimensions['height'] . '" src="' . $src . '" 
     frameborder="0" allowfullscreen></iframe>';
 
+  if ($size == 'responsive') {
+    $output = '<div class="youtube-container--responsive">' . $output . '</div>';
+  }
+
   return $output;
 }