The purpose of this study was to investigate changes in blood pressure and renal function after percutaneous renal artery balloon angioplasty in hypertensive patients with atherosclerotic renal artery stenosis. Renal artery lesions were assessed by duplex ultrasound before and after renal artery balloon angioplasty. Renal arteries were classified as normal, < 60% stenosis, > or =60% stenosis, and occluded according to previously validated duplex criteria. Data regarding risk factors for atherosclerosis and years of hypertension were collected. Systolic and diastolic blood pressure, creatinine, and number of medications were obtained before and after intervention. The immediate technical outcome of renal artery angioplasty was classified based on the arteriographic result as follows: success (residual stenosis < or =30%), partial success (residual stenosis 31-50%), or unsuccessful (residual stenosis > 50%). For bilateral procedures, success required both renal arteries to be classified as technical successes; a technical success on one side only was classified as partial success. The blood pressure response to intervention was classified as follows: cure (diastolic blood pressure < or =95 mm Hg on no medications), improved (control of blood pressure with a significant reduction in number of medications or control of previously elevated blood pressure without a change in medications), or failed (all other responses). The study group included 28 patients (14 men, 14 women) with a mean age of 65 years. The preintervention and the first postintervention evaluations occurred within 180 days of the procedure. All patients were hypertensive, and all except one were under medical treatment. Mean duration of hypertension was 9.1 +/-8.8 years. There were 38 interventional procedures (28 unilateral, 10 bilateral) involving 41 renal arteries; seven arteries had two procedures done. Before angioplasty, all renal arteries had lesions of > or =60% diameter reduction by duplex scanning. Endovascular stents were deployed following angioplasty in 14 (34%) of the procedures. The technical result was classified as a success in 24 (63%), a partial success in 12 (32%) of the procedures, and two procedures (5%) were classed as technical failures. There were statistically significant reductions in blood pressure following successful and partially successful procedures, but cure of hypertension was achieved in only 11% of cases. There were no significant changes in creatinine in any of the technical result groups. Of the 38 renal arteries evaluated with duplex ultrasound following intervention, 39% were found to have stenosis of > or =0% involving a treated renal artery, including one postintervention occlusion. Cure of hypertension was rare in this patient population with atherosclerotic renal artery stenosis. More than one third of the treated renal arteries showed > or =0% lesions recurring after the procedure. Thirteen percent of those with technical success and 17% of those with partial technical success had creatinine improvement of at least 20% over the baseline value. Significant clinical and anatomic improvement were relatively uncommon following balloon angioplasty in this series of patients.