The frequency of noncompliance with postoperative medical therapy ranges from 2% to 43% in organ transplant recipients and causes more graft loss than uncontrolled rejection in compliant patients. Retrospective and prospective studies undertaken at our center showed no difference in the rate of noncompliance between males and females or between recipients of cadaveric kidneys and those from living, related donors. Patients less than 20 years of age were statistically the most noncompliant (p = 0.0001) compared with those over 40 years. A significant difference in compliance was seen among blacks, Hispanics, and non-Hispanic whites, with the greatest frequency in blacks. This was not due to race, but to socioeconomic status, with those in the low socioeconomic group the most noncompliant. Problems of noncompliance may be reduced if they are identified early in the treatment course.