Program impact methodology--usually referred to as evaluation research--is described as it is developing in the United States. Several problems face the field of evaluation research. First, those issues grouped as "meta-scientific" include: (1) the distinction between qualitative and quantitative studies; (2) the separation of implementation and…

In spite of many inherent problems, impact evaluation should remain an integral part of program evaluation, both because impact evaluation brings its budget justification with it, and because its focus on causal hypotheses is an essential part of evaluation. Methodology based on the author's body of work is reviewed. (SLD)