It is a special characteristic of all modern societies that we consciously decide on and plan projects designed to improve our social systems. It is our universal predicament that our projects do not always have their intended effects. Very probably we all share in the experience that often we cannot tell whether the project had any impact at all, so complex is the flux of historical changes that would have been going on anyway, and so many are the other projects that might be expected to modify the same indicators. It seems inevitable that in most countries this common set of problems, combined with the obvious relevance of social science research procedures, will have generated a methodology and methodological specialists focused on the problem of assessing the impact of planned social change. It is an assumption if this paper that, in spite of differences in the forms of government and approaches to social planning and problem-solving, much of this methodology can be usefully shared — that social project evaluation methodology is one of the fields of science that has enough universality to make scientific sharing mutually beneficial. As a part of this sharing, this paper reports on program impact assessment methodology as it is developing in the United States today.