Many examples illustrate the usefulness of group partitioning in distributed systems. The process group abstraction is a powerful tool for the development of fault-tolerant distributed applications. This solution is also particularly relevant to group entities sharing similar properties or stakes when applied to the field of cooperative work. When dealing with distributed applications, communication standards have evolved from socket-based interfaces to Remote Procedure Calls and nowadays, towards distributed object platforms like CORBA. This standard from the Object Management Group masks distribution and heterogeneity and provides a good basis for distributed application development. This paper presents a review of group mechanisms found in the literature then focuses on the implementation of groups over CORBA. An implementation of such a service over CORBA illustrates the impact of group auto-organization. Performance we obtain show that our service is efficient and provides good mechanisms to manage operations in a group.