This report describes the evolution of an evaluation unit organized to assess the impact of a changing hospital care program upon the community it serves. Evaluation activities have been developed to suit the specific characteristics of the program to be evaluated and also to provide continuous, in contrast to single-shot, appraisals of programmatic change. Methodological problems encountered in defining and developing the overall program of evaluation are reviewed. The rationale for the organization of a clinical assessment team— one of the component evaluation activities—is also described.