Efforts were made in the Beta Blocker Heart Trial (BHAT), a double-blind study of 3837 post-MI patients, to enhance visit adherence, a measure of compliance that is not subjective and can be easily monitored. Of the required visits, 93.9% were completed in the window, 3.9% of the patients were classified as dropouts and 12 persons were lost to follow-up. Methods used to enhance compliance varied with circumstances but included appointment reminders, assistance with transportation, minimal waiting times, newsletters, continuity of care, involvement of family members, and close contact with private physicians. Comparisons of the BHAT visit adherence rates to those from other clinical trials are difficult to make because there are few reports in the literature regarding follow-up in large multicenter clinical trials. However, data obtained through personal communications, as well as published reports, indicate that adherence in primary prevention trials was generally less than that of secondary prevention trials. Adherence rates in the BHAT tended to be slightly higher than those of comparable trials.