One of the difficulties in social work lies in finding forms of evaluation that suit the various kinds of work people actually do. There is a need for methods that allow a valid and rigorous evaluation of process as well as outcomes, particularly in new areas of work. A valuable example of such evaluation evolved at St. Luke's, a voluntary agency in Victoria, Australia, that used design evaluation to articulate a new model of practice. Design evaluation involved having the evaluator work with staff to describe work practices as a series of stages with associated principles. This process of documenting, clarifying, and illuminating the model led to its progressive refinement and concurrent improved services delivery to clients. Testing the program model with clients provided some valuable feedback about its effectiveness. This form of evaluation is complementary to outcomes evaluation and can also provide the information needed for a subsequent outcomes evaluation.