We are in the same situation. Have been using EJB 2.1 SLSB and MDB for a while on jboss 4.0.5. Now we want to use ejb3 for new development. Are there any guidelines on how to deploy a mix of two. Should we use "ejb3" configuration from jboss 4.0.5 installation if we want to mix the two? Do ejb 2.1 and ejb3 beans need to be in separate jars? can they be in the same ear? I tried by installing "ejb3" configuration off jboss 4.0.5 and deploying my old ejb2.1 jar/ear under it. Quick testing showed no problem. Then I tried adding a sample ejb3 SLSB to the same jar/ear and deploying is giving following error.. 10:19:14,196 WARN [ServiceController] Problem creating service jboss.j2ee:service=EJB3,module=MyApp.jar | java.lang.NoSuchMethodException: com.mycompany.enms.cluster.ClusterManagerBean.remove() | at java.lang.Class.getMethod(Class.java:1581) | at org.jboss.ejb3.Ejb3DescriptorHandler.addAnnotations(Ejb3DescriptorHandler.java:1800) | at org.jboss.ejb3.Ejb3DescriptorHandler.addSecurityAnnotations(Ejb3DescriptorHandler.java:770) | at org.jboss.ejb3.Ejb3DescriptorHandler.addDescriptorAnnotations(Ejb3DescriptorHandler.java:613) | at org.jboss.ejb3.Ejb3DescriptorHandler.getStatelessContainer(Ejb3DescriptorHandler.java:309) | at org.jboss.ejb3.Ejb3AnnotationHandler.getContainers(Ejb3AnnotationHandler.java:130) | at org.jboss.ejb3.Ejb3Deployment.deployElement(Ejb3Deployment.java:409) | at org.jboss.ejb3.Ejb3Deployment.deployElement(Ejb3Deployment.java:397) | at org.jboss.ejb3.Ejb3Deployment.deployUrl(Ejb3Deployment.java:378) | .... | .... View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4000496#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...