diff --git a/src/main/scala/app/UserManagementController.scala b/src/main/scala/app/UserManagementController.scala
index f3ff60b..f625126 100644
--- a/src/main/scala/app/UserManagementController.scala
+++ b/src/main/scala/app/UserManagementController.scala
@@ -5,27 +5,32 @@
 import util.StringUtil._
 import jp.sf.amateras.scalatra.forms._
 
-class UserManagementController extends UserManagementControllerBase with AccountService with AdminAuthenticator
+class UserManagementController extends UserManagementControllerBase
+  with AccountService with RepositoryService with AdminAuthenticator
 
 trait UserManagementControllerBase extends AccountManagementControllerBase {
-  self: AccountService with AdminAuthenticator =>
+  self: AccountService with RepositoryService with AdminAuthenticator =>
   
-  case class UserNewForm(userName: String, password: String, mailAddress: String, isAdmin: Boolean,
+  case class NewUserForm(userName: String, password: String, mailAddress: String, isAdmin: Boolean,
                          url: Option[String], fileId: Option[String])
 
-  case class UserEditForm(userName: String, password: Option[String], mailAddress: String, isAdmin: Boolean,
+  case class EditUserForm(userName: String, password: Option[String], mailAddress: String, isAdmin: Boolean,
                           url: Option[String], fileId: Option[String], clearImage: Boolean)
 
-  val newForm = mapping(
+  case class NewGroupForm(groupName: String, fileId: Option[String], memberNames: Option[String])
+
+  case class EditGroupForm(groupName: String, fileId: Option[String], memberNames: Option[String], clearImage: Boolean)
+
+  val newUserForm = mapping(
     "userName"    -> trim(label("Username"     , text(required, maxlength(100), identifier, uniqueUserName))),
     "password"    -> trim(label("Password"     , text(required, maxlength(20)))),
     "mailAddress" -> trim(label("Mail Address" , text(required, maxlength(100), uniqueMailAddress()))),
     "isAdmin"     -> trim(label("User Type"    , boolean())),
     "url"         -> trim(label("URL"          , optional(text(maxlength(200))))),
     "fileId"      -> trim(label("File ID"      , optional(text())))
-  )(UserNewForm.apply)
+  )(NewUserForm.apply)
 
-  val editForm = mapping(
+  val editUserForm = mapping(
     "userName"    -> trim(label("Username"     , text(required, maxlength(100), identifier))),
     "password"    -> trim(label("Password"     , optional(text(maxlength(20))))),
     "mailAddress" -> trim(label("Mail Address" , text(required, maxlength(100), uniqueMailAddress("userName")))),
@@ -33,8 +38,21 @@
     "url"         -> trim(label("URL"          , optional(text(maxlength(200))))),
     "fileId"      -> trim(label("File ID"      , optional(text()))),
     "clearImage"  -> trim(label("Clear image"  , boolean()))
-  )(UserEditForm.apply)
-  
+  )(EditUserForm.apply)
+
+  val newGroupForm = mapping(
+    "groupName"   -> trim(label("Group name"   , text(required, maxlength(100), identifier))),
+    "fileId"      -> trim(label("File ID"      , optional(text()))),
+    "memberNames" -> trim(label("Member Names" , optional(text())))
+  )(NewGroupForm.apply)
+
+  val editGroupForm = mapping(
+    "groupName"   -> trim(label("Group name"   , text(required, maxlength(100), identifier))),
+    "fileId"      -> trim(label("File ID"      , optional(text()))),
+    "memberNames" -> trim(label("Member Names" , optional(text()))),
+    "clearImage"  -> trim(label("Clear image"  , boolean()))
+  )(EditGroupForm.apply)
+
   get("/admin/users")(adminOnly {
     admin.users.html.list(getAllUsers())
   })
@@ -43,7 +61,7 @@
     admin.users.html.edit(None)
   })
   
-  post("/admin/users/_new", newForm)(adminOnly { form =>
+  post("/admin/users/_new", newUserForm)(adminOnly { form =>
     createAccount(form.userName, sha1(form.password), form.mailAddress, form.isAdmin, form.url)
     updateImage(form.userName, form.fileId, false)
     redirect("/admin/users")
@@ -54,7 +72,7 @@
     admin.users.html.edit(getAccountByUserName(userName))
   })
   
-  post("/admin/users/:name/_edit", editForm)(adminOnly { form =>
+  post("/admin/users/:name/_edit", editUserForm)(adminOnly { form =>
     val userName = params("userName")
     getAccountByUserName(userName).map { account =>
       updateAccount(getAccountByUserName(userName).get.copy(
@@ -69,9 +87,40 @@
     } getOrElse NotFound
   })
 
-  get("/admin/users/_newgroup"){
-    admin.users.html.group(None)
-  }
+  get("/admin/users/_newgroup")(adminOnly {
+    admin.users.html.group(None, Nil)
+  })
+
+  post("/admin/users/_newgroup", newGroupForm)(adminOnly { form =>
+    createGroup(form.groupName)
+    updateGroupMembers(form.groupName, form.memberNames.map(_.split(",").toList).getOrElse(Nil))
+    updateImage(form.groupName, form.fileId, false)
+    redirect("/admin/users")
+  })
+
+  get("/admin/users/:groupName/_editgroup")(adminOnly {
+    val groupName = params("groupName")
+    admin.users.html.group(getAccountByUserName(groupName), getGroupMembers(groupName))
+  })
+
+  post("/admin/users/:groupName/_editgroup", editGroupForm)(adminOnly { form =>
+    val groupName = params("groupName")
+    getAccountByUserName(groupName).map { account =>
+      val memberNames = form.memberNames.map(_.split(",").toList).getOrElse(Nil)
+      updateGroupMembers(form.groupName, memberNames)
+
+      getRepositoryNamesOfUser(form.groupName).foreach { repositoryName =>
+        removeCollaborators(form.groupName, repositoryName)
+        memberNames.foreach { userName =>
+          addCollaborator(form.groupName, repositoryName, userName)
+        }
+      }
+
+      updateImage(form.groupName, form.fileId, form.clearImage)
+      redirect("/admin/users")
+
+    } getOrElse NotFound
+  })
 
   /**
    * JSON API for collaborator completion.
diff --git a/src/main/scala/service/AccountService.scala b/src/main/scala/service/AccountService.scala
index eae2949..5a9aea3 100644
--- a/src/main/scala/service/AccountService.scala
+++ b/src/main/scala/service/AccountService.scala
@@ -45,5 +45,33 @@
 
   def updateLastLoginDate(userName: String): Unit =
     Accounts.filter(_.userName is userName.bind).map(_.lastLoginDate).update(currentDate)
-  
+
+  def createGroup(groupName: String): Unit =
+    Accounts insert Account(
+      userName       = groupName,
+      password       = "",
+      mailAddress    = "",
+      isAdmin        = false,
+      url            = None,
+      registeredDate = currentDate,
+      updatedDate    = currentDate,
+      lastLoginDate  = None,
+      image          = None,
+      isGroupAccount = true)
+
+  def updateGroupMembers(groupName: String, members: List[String]): Unit = {
+    Query(GroupMembers).filter(_.groupName is groupName.bind).delete
+
+    members.foreach { userName =>
+      GroupMembers insert GroupMember (groupName, userName)
+    }
+  }
+
+  def getGroupMembers(groupName: String): List[String] =
+    Query(GroupMembers)
+      .filter(_.groupName is groupName.bind)
+      .sortBy(_.userName)
+      .map(_.userName)
+      .list
+
 }
diff --git a/src/main/scala/service/RepositoryService.scala b/src/main/scala/service/RepositoryService.scala
index 153aa95..b8c7596 100644
--- a/src/main/scala/service/RepositoryService.scala
+++ b/src/main/scala/service/RepositoryService.scala
@@ -162,6 +162,15 @@
     Collaborators.filter(_.byPrimaryKey(userName, repositoryName, collaboratorName)).delete
 
   /**
+   * Remove all collaborators from the repository.
+   *
+   * @param userName the user name of the repository owner
+   * @param repositoryName the repository name
+   */
+  def removeCollaborators(userName: String, repositoryName: String): Unit =
+    Collaborators.filter(_.byRepository(userName, repositoryName)).delete
+
+  /**
    * Returns the list of collaborators name which is sorted with ascending order.
    * 
    * @param userName the user name of the repository owner
diff --git a/src/main/twirl/admin/users/group.scala.html b/src/main/twirl/admin/users/group.scala.html
index da55c0b..0fdfbd7 100644
--- a/src/main/twirl/admin/users/group.scala.html
+++ b/src/main/twirl/admin/users/group.scala.html
@@ -1,15 +1,15 @@
-@(account: Option[model.Account])(implicit context: app.Context)
+@(account: Option[model.Account], members: List[String])(implicit context: app.Context)
 @import context._
 @import view.helpers._
 @html.main(if(account.isEmpty) "New User" else "Update User"){
   @admin.html.menu("users"){
-    <form method="POST" action="@if(account.isEmpty){@path/admin/users/_new} else {@path/admin/users/@account.get.userName/_edit}" validate="true">
+    <form method="POST" action="@if(account.isEmpty){@path/admin/users/_newgroup} else {@path/admin/users/@account.get.userName/_editgroup}" validate="true">
       <div class="row-fluid">
         <div class="span5">
           <fieldset>
-            <label for="userName"><strong>Group name</strong></label>
-            <input type="text" name="userName" id="userName" value="@account.map(_.userName)"@if(account.isDefined){ readonly}/>
-            <span id="error-userName" class="error"></span>
+            <label for="groupName"><strong>Group name</strong></label>
+            <input type="text" name="groupName" id="groupName" value="@account.map(_.userName)"@if(account.isDefined){ readonly}/>
+            <span id="error-groupName" class="error"></span>
           </fieldset>
           <fieldset>
             <label for="avatar"><strong>Image (Optional)</strong></label>
@@ -20,14 +20,22 @@
           <fieldset>
             <label><strong>Members</strong></label>
             <ul id="members" class="collaborator">
+              @members.map { userName =>
+                <li data-userName="@userName">
+                  <a href="@path/@url(userName)">@userName</a>
+                  <a href="#" class="remove">(remove)</a>
+                </li>
+              }
             </ul>
             <input type="text" id="memberName" style="width: 300px; margin-bottom: 0px;"/>
-            <input type="button" class="btn" value="Add" id="addMember">
+            <input type="button" class="btn" value="Add" id="addMember"/>
+            <input type="hidden" id="memberNames" name="memberNames" value=""/>
+            <span class="error" id="error-memberName"></span>
           </fieldset>
         </div>
       </div>
       <fieldset class="margin">
-        <input type="submit" class="btn btn-success" value="@if(account.isEmpty){Create Group} else {Update Group}"/>
+        <input type="submit" class="btn btn-success" id="submit" value="@if(account.isEmpty){Create Group} else {Update Group}"/>
         <a href="@path/admin/users" class="btn">Cancel</a>
       </fieldset>
     </form>
@@ -45,9 +53,23 @@
   });
 
   $('#addMember').click(function(){
+    $('#error-memberName').text('');
     var userName = $('#memberName').val();
+
+    // TODO check existence
+
+    // check duplication
+    var exists = $('#members li').filter(function(){
+      return $(this).data('userName') == userName;
+    }).length > 0;
+    if(exists){
+      $('#error-memberName').text('User has been already added.');
+      return false;
+    }
+
     $('#members').append($('<li>')
-      .append($('<a>').attr('href', '#').text(userName))
+      .data('userName', userName)
+      .append($('<a>').attr('href', '@path/' + userName).text(userName))
       .append(' ')
       .append($('<a>').attr('href', '#').addClass('remove').text('(remove)')));
     $('#memberName').val('');
@@ -56,5 +78,13 @@
   $(document).on('click', '.remove', function(){
     $(this).parent().remove();
   });
+
+  $('#submit').click(function(){
+    var userNames = $('#members li').map(function(i, e){
+      return $(e).data('userName');
+    }).get().join(',');
+    $('#memberNames').val(userNames);
+    return true;
+  });
 });
 </script>
\ No newline at end of file
diff --git a/src/main/twirl/admin/users/list.scala.html b/src/main/twirl/admin/users/list.scala.html
index 70fe434..e73d0fa 100644
--- a/src/main/twirl/admin/users/list.scala.html
+++ b/src/main/twirl/admin/users/list.scala.html
@@ -12,28 +12,40 @@
         <tr>
           <td>
             <div class="pull-right">
-              <a href="@path/admin/users/@account.userName/_edit">Edit</a>
+              @if(account.isGroupAccount){
+                <a href="@path/admin/users/@account.userName/_editgroup">Edit</a>
+              } else {
+                <a href="@path/admin/users/@account.userName/_edit">Edit</a>
+              }
             </div>
             <div class="strong">
               @avatar(account.userName, 20)
               <a href="@url(account.userName)">@account.userName</a>
-              @if(account.isAdmin){
-                (Administrator)
+              @if(account.isGroupAccount){
+                (Group)
               } else {
-                (Normal)
+                @if(account.isAdmin){
+                  (Administrator)
+                } else {
+                  (Normal)
+                }
               }
             </div>
             <div>
               <hr>
-              <i class="icon-envelope"></i> @account.mailAddress
-              @account.url.map { url =>
-                <i class="icon-home"></i> @url
+              @if(!account.isGroupAccount){
+                <i class="icon-envelope"></i> @account.mailAddress
+                @account.url.map { url =>
+                  <i class="icon-home"></i> @url
+                }
               }
             </div>
             <div>
               <span class="muted">Registered:</span> @datetime(account.registeredDate)
               <span class="muted">Updated:</span> @datetime(account.updatedDate)
-              <span class="muted">Last Login:</span> @account.lastLoginDate.map(datetime)
+              @if(!account.isGroupAccount){
+                <span class="muted">Last Login:</span> @account.lastLoginDate.map(datetime)
+              }
             </div>
           </td>
         </tr>