F ORMAL organizations are organized to JL achieve a set of objectives. They are believed to be more efhcient than any other form of organization of activities because they create conditions which facilitate optimal attainment of objectives. These conditions include throughput processesdivision of work (or organization of units), decision-making, communication, coordination, leadership, feedback, etc. Thus, designing of organization involves the grouping of activities or what Lawrence and Lorsch call differentiation (1976: 141-165)~ developing integrative mechanisms (or coordination), decision-making structure (centralized or decentralized), delineation of work procedures (flexible or rigid), etc. This paper has two purposes: ( 1 ) To develop an analytical framework for the development of organizational designs by integrating existing theories and concepts and (2) to apply the analytical framework in proposing organizational design models for human service organizations.The classical organization theorists devoted a great deal of effort in determining the principles for division of work in organizations. Gulick and Urwick, for example, identified four bases, useful in determining work units: (1) The major purpose, (2) the process to be used, (3) the clienteles to be served and (4) the place where the activities will take place (1937: 15-30). The main idea in using these bases is to combine homogenous units and to separate heterogenous ones.A review of the works of the prominent writers in the management science reveals the commonly cited bases of division of activities in the organization are purpose and f unction. Under the former the units are organized on the basis of products; and specialists engaged in its production report to the product unit manager who, in turn, reports to the general manager. In the latter, the units are organized on the basis of functions : sales, manufacturing, engin'eering, finance, etc.; and the functional managers are responsible to the general manager. Thus, each functional unit serves all line departments.The question : when should one use product or function as a basis for designing work structure? -has consistently troubled the administrators. Lawrence and Lorsch observe that each unit should have an organization design which fits its particular external environment and its members' predispositions because of relationship between organization design and the behaviors of the members working in it.