FORMAL, SYSTEMATIC SOCIAL SCIENCE RESEARCH ON THE EFFECTIVENESS OF PUBLIC POLICY HAS BECOME INCREASINGLY USED IN THE LAST TWO DECADES AS POLICY MAKERS HAVE BECOME INCREASINGLY SKEPTICAL ABOUT THE EFFECTIVENESS OF PUBLIC POLICY, ESPECIALLY IN THE SOCIAL WELFARE AREAS. A SURVEY OF EXISTING RESEARCH DESIGNS AND ACCOMPANYING TECHNIQUES IS PRESENTED ALONG WITH BRIEF ASSESSMENTS OF THEIR USEFULNESS FOR PROGRAMS OF DIFFERENT TYPES. THE AUTHORS STRESS PARTICULARLY THE USE OF FIELD EXPERIMENTS FOR THE ASSESSMENT OF PROSPECTIVE SOCIAL POLICIES AND PROGRAMS. (AUTHOR ABSTRACT)...BS