Results of medical and surgical treatment of renovascular hypertension were compared retrospectively in 28 patients. Renal function remained normal throughout the study in all patients. After six months of follow-up, systolic and diastolic blood pressures were significantly lower in the 15 patients treated surgically than in the 13 patients treated medically. At 12 months however, a significant difference could be demonstrated only for systolic blood pressure and at 24 and 36 months, no difference in systolic or diastolic pressure could be demonstrated between the two groups. This failure to find a significant difference between surgical and medical therapy resulted from return of hypertension among the patients in the surgical group with arteriosclerotic renovascular hypertension; 6 of 7 patients with fibromuscular dysplasia as the etiology of the renovascular hypertension were cured by surgery and none of these relapsed during follow-up. All patients with arteriosclerotic renovascular disease who were operated upon required medication for the control of their blood pressure within 12 months after operation. The findings in this retrospective study emphasize the importance of prolonged follow-up when assessing the value of different therapies in renovascular hypertension and provide evidence indicating that medical management is acceptable and appropriate, particularly for high risk patients. The results also force recognition of the need for a randomized prospective trial of medical and surgical therapy in arteriosclerotic renovascular hypertension.