The development of efficient agent-based medical diagnosis systems represents a recent research direction. Medical multiagent systems may improve the efficiency of traditionally developed medical computational systems, like the medical expert systems. In this paper, is proposed a novel cooperative hybrid medical diagnosis multiagent system called CMDS. The cooperative problem solving by the proposed medical system combine the physicians and artificial agents advantages in the medical diagnoses elaborations, by using efficiently the medical knowledge distributed between the members of the system. The novelty consists in the use of a novel class of medical agents, called medical expert system agents and a novel cooperative medical problems solving by the system's members. CMDS system can solve flexibly a large variety of medical diagnosis problems.