diff --git a/wp-admin/ms-edit.php b/wp-admin/ms-edit.php
index e20b89ae55..fbc28e4505 100644
--- a/wp-admin/ms-edit.php
+++ b/wp-admin/ms-edit.php
@@ -167,7 +167,7 @@ switch ( $_GET['action'] ) {
 			wp_die( __( 'Invalid email address.' ) );
 
 		if ( is_subdomain_install() ) {
-			$newdomain = $domain . '.' . $current_site->domain;
+			$newdomain = $domain . '.' . preg_replace( '|^www\.|', '', $current_site->domain );
 			$path = $base;
 		} else {
 			$newdomain = $current_site->domain;
diff --git a/wp-admin/ms-sites.php b/wp-admin/ms-sites.php
index 989d2c1214..1576046746 100644
--- a/wp-admin/ms-sites.php
+++ b/wp-admin/ms-sites.php
@@ -714,7 +714,7 @@ switch ( $action ) {
 						<th scope="row"><?php _e( 'Site Address' ) ?></th>
 						<td>
 						<?php if ( is_subdomain_install() ) { ?>
-							<input name="blog[domain]" type="text" class="regular-text" title="<?php _e( 'Domain' ) ?>"/>.<?php echo $current_site->domain;?>
+							<input name="blog[domain]" type="text" class="regular-text" title="<?php _e( 'Domain' ) ?>"/>.<?php echo preg_replace( '|^www\.|', '', $current_site->domain );?>
 						<?php } else {
 							echo $current_site->domain . $current_site->path ?><input name="blog[domain]" class="regular-text" type="text" title="<?php _e( 'Domain' ) ?>"/>
 						<?php }
diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index b3837f7720..2ca7e4ea85 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -597,7 +597,7 @@ function wpmu_validate_blog_signup($blogname, $blog_title, $user = '') {
 
 	// Check if the domain/path has been used already.
 	if ( is_subdomain_install() ) {
-		$mydomain = "$blogname.$domain";
+		$mydomain = $blogname . '.' . preg_replace( '|^www\.|', '', $domain );
 		$path = $base;
 	} else {
 		$mydomain = "$domain";
diff --git a/wp-signup.php b/wp-signup.php
index f59804b68a..cc204a4cca 100644
--- a/wp-signup.php
+++ b/wp-signup.php
@@ -78,15 +78,15 @@ function show_blog_form($blogname = '', $blog_title = '', $errors = '') {
 	if ( !is_subdomain_install() )
 		echo '<span class="prefix_address">' . $current_site->domain . $current_site->path . '</span><input name="blogname" type="text" id="blogname" value="'. esc_attr($blogname) .'" maxlength="50" /><br />';
 	else
-		echo '<input name="blogname" type="text" id="blogname" value="'.esc_attr($blogname).'" maxlength="50" /><span class="suffix_address">.' . $current_site->domain . '</span><br />';
+		echo '<input name="blogname" type="text" id="blogname" value="'.esc_attr($blogname).'" maxlength="50" /><span class="suffix_address">.' . ( $site_domain = preg_replace( '|^www\.|', '', $current_site->domain ) ) . '</span><br />';
 
 	if ( !is_user_logged_in() ) {
 		print '(<strong>' . __( 'Your address will be ' );
 		if ( !is_subdomain_install() )
 			print $current_site->domain . $current_site->path . __( 'sitename' );
 		else
-			print __( 'domain.' ) . $current_site->domain . $current_site->path;
-		echo '.)</strong> ' . __( 'Must be at least 4 characters, letters and numbers only. It cannot be changed, so choose carefully!' ) . '</p>';
+			print __( 'domain.' ) . $site_domain . $current_site->path;
+		echo '.</strong>) ' . __( 'Must be at least 4 characters, letters and numbers only. It cannot be changed, so choose carefully!' ) . '</p>';
 	}
 
 	// Blog Title