A brief review of systems theory provides a rationale for an underlying theoretical model within which systems theory can be more completely understood. The essence of the model is that persons are the major unit of study because the available means of satisfying "basic needs" define and shape interaction patterns in the family as in other human subsets. The basis for the need systems derives from existential theory/philosophy and utilizes a substantial part of Erich Fromm's formulations. The ecological model of family therapy studies all interacting forces that influence a family such as interpersonal, intrapersonal, cultural, political, and economical. The major therapeutic technique is to develop awareness of the forces interacting in a family and assist the family to make changes through a sequential process of (1) understanding, (2) exploration of alternatives, (3) implementation of changes, (4) stabilization, and (5) establishment of support systems. (Author)