When two separate and independent organizations must work together to accomplish a mutual task, difficulties often arise which remain poorly understood. The analysis of intergroup phenomena involves an exploration of interaction within and between groups; such relationships include problems arising from differences in tasks, structure, and culture of the two groups, definition of the intergroup task, choice of group representatives, and the possibilities and problems of dual group membership for the negotiators. While the literatures on group process and organization development contain some work on intergroup phenomena (e.g., Aldrich, 1971; Baker and O'Brien, 1971; Klein et al., 1971; Mills, 1975; Walton, 1972), much conceptual work remains to be done. We will focus upon one type of intergroup relationship--that between a traditional human service organization and a social movement group--in which dual membership is a particular problem, and in which conflict may be neutralized by the form of the negotiations. A case example of an interaction between a mental health center and a women's liberation group will provide one example of such negotiations. The analysis is presented within the framework of the open system model of Miller and Rice (1967) and Rice's general model of intergroup relations (1965, 1969).