The objective was to identify subgroups of patients with hypertension and atherosclerotic renal artery stenosis who may benefit from immediate intervention. In the DRASTIC study, patients with hypertension, significant atherosclerotic renal artery stenosis, and a normal or mildly impaired renal function were randomized between immediate balloon angioplasty (PTRA; n = 56) and drug therapy followed by angioplasty after 3 months, if needed (Med-PTRA; n = 50). In this secondary analysis of the data, changes in the renal function and blood pressure after 1 year were studied by analysis of covariance in the following subgroups: patients with positive captopril-renin challenge test, abnormal captopril renogram, recently developed hypertension, bilateral stenosis, and severe stenosis. We found a benefit of immediate angioplasty only for patients with bilateral stenosis. Their creatinine clearance had decreased (mean ± s.d.: -4.2 ± 13.5 ml/min) in the Med-PTRA group, whereas it had improved substantially (+10.0 ± 15.7 ml/min) in the PTRA group (P=0.02). For patients with unilateral stenosis, the change in creatinine clearance did not differ between PTRA and Med-PTRA (+4.3 ± 15.5 and +1.3 ± 12.5 ml/min, respectively). The patients with bilateral stenosis also seemed to benefit most from immediate intervention with regard to blood pressure control. None of the other subgroups had a clear benefit of immediate intervention regarding renal function or blood pressure control. In conclusion, intervention should not be postponed in patients with bilateral stenosis, even if renal function is normal. Other hypertensive patients with atherosclerotic renal artery disease could initially well be treated by aggressive multidrug therapy alone unless hypertension persists or renal function deteriorates.