A study of 17 hospitals in the Greater Delaware Valley region was undertaken in order to determine if those hospitals which had participated in an early voluntary effort to initiate medical audit differed qualitatively or quantitatively from a matched group of hospitals which had not participated in the previous project. The study also provided the opportunity to analyze the current status of medical audit in a group of hospitals which varied significantly in size, location, and educational responsibilities. Data regarding audit administrative organization, number of audits performed, type of system used, quality of audit criteria, and utilization of audit findings were gathered and analyzed. For these variables, no discernible differences were found between hospitals which had participated in the early voluntary project and those which had not. Wide variations were found among the hospitals in the extent to which medical audit processes were formalized and implemented. There were also variations in the quality of criteria formulated by the hospitals, but they generally did not receive a high rating. The implications of audit findings were generally not followed up in an organized and appropriate manner. Many hospitals which had received PSRO delegated status were given a low rating by the reviewers. The implications of these findings are discussed.