Abstract : This thesis subject is support for distributed cooperative applications. The concept of processus groups, using message passing to communicate is one of the prime mechanism used to build such applications. A State of the Art browse the various semantics and the main implementations of such protocols. Le protocol selected for the implementation is based on the Amoeba one's, modified to support opaque groups. Various optimizations have also been added. The implementation is based on a generic layer, encapsulating all the low level needs provided by the system, this proved useful to extend or build new protocols. The first implementation was running at user-level on top of Mach 3.0 micro-kernel, and was followed by port on various Unix systems. This thesis provides an in-depth analysis of the protocol performances, and the impact of various protocol parameters. Last but not least, a fine-tuned study of protocol execution located in user mode finish to validate the implementation choices.