The Certified Hospital Admission Program (CHAP), which was originated by the Medical Care Foundation of Sacramento, California, is regarded as a prototype of admission certification programs and the concurrent monitoring of inpatient care. These peer review functions have now been made key elements of provider utilization review requirements and of Professional Standards Review Organizations' program operations for Medicare and Medicaid. The present article questions, on methodological and interpretive grounds, earlier published findings and conclusions about CHAP's effectiveness. Significant deficiencies in evaluating its impact may mean that the success of CHAP has not yet been demonstrated and, hence, that an adequate basis for formulating certain national peer review policies may not exist.