Three health science library organizations are briefly discussed. The organizations are: (1) Metropolitan Detroit Medical Library Group, (2) Health Science Librarians of Northwest Ohio, and (3) Medical Library Association of Northern Ohio. This paper provides a perspective in which to report the efforts the three groups have made to improve library service. The efforts are experiments in social organization of library systems and networks. The organizations have the following characteristics in common: (1) they are located within metropolitan areas, (2) the groups have demonstrated a stability and continuity, (3) each of the groups has as one of its members a resource library, and (4) collective action by the group has produced demonstrable results affecting the kind and quality of service throughout their areas. (MF)