Index: dbLearnStar-webApp/src/main/java/dblearnstar/webapp/pages/admin/GroupManagement.java
===================================================================
--- dbLearnStar-webApp/src/main/java/dblearnstar/webapp/pages/admin/GroupManagement.java	(revision 717f87ed1469d948a29cee2fce6a95421da132af)
+++ dbLearnStar-webApp/src/main/java/dblearnstar/webapp/pages/admin/GroupManagement.java	(revision f1d5a553f268ede4675b5f2b4905d297b813cd2f)
@@ -144,8 +144,11 @@
 								.getStudentsByPersonId(personManager.getPersonByUsername(lineField).getPersonId())
 								.get(0);
-						GroupMember gm = new GroupMember();
-						gm.setGroup(editGroup);
-						gm.setStudent(s);
-						genericService.save(gm);
+						if (editGroup.getGroupMembers().stream()
+								.noneMatch(p -> p.getStudent().getStudentId() == s.getStudentId())) {
+							GroupMember gm = new GroupMember();
+							gm.setGroup(editGroup);
+							gm.setStudent(s);
+							genericService.save(gm);
+						}
 					} catch (Exception e) {
 						errors += ">>> Student " + line + " can not be imported due to: " + e.getLocalizedMessage();
@@ -280,5 +283,5 @@
 			}
 		}
-		groupCopyFrom=null;
+		groupCopyFrom = null;
 	}
 }