A telephone survey of 602 randomly selected hospitals was conducted to identify existing ethics committees, i.e., those with the potential to become involved in the decision-making process in specific cases. Using the number of acute care beds as the criterion, hospitals were divided into 2 groups: (1) over 200 beds; n = 400; (2) 200 or fewer beds; n = 202. Chairpersons of identified committees completed detailed questionnaires. Seventeen committees were found--approximately 1% of all U.S. hospitals. A typical committee included physicians, clergymen, and other professionals. Almost all committees were advisory, not decision-making bodies, and considered very effective by their chairpersons. Ethics committees have not, however, solved current medical ethical problems; nor have they allayed the concerns of patients' rights advocates about patient representation and control. Further study is warranted.