Investigations for renal artery stenosis have been greatly facilitated by advances in imaging techniques. Intravenous digital subtraction angiography is now performed in all patients with progressive, drug-resistant hypertension associated with aorto-iliac lesions or with renal impairment induced by angiotensin-converting enzyme inhibitors. Yet the finding of hypertension with renal artery stenosis is not enough to make the diagnosis of renovascular hypertension, this term being reserved to hypertension reversible by revascularization. The selection of patients who may benefit from revascularization rests on urography to explore the excretory and endocrine functions of the ischaemic kidney, as well as on scintigraphy and measurement of renin levels in renal veins before and after administration of captopril. The functional data are completed by vascular exploration which helps in evaluating the usefulness and safety of revascularization: repercussions of hypertension on target organs and extension of the vascular disease to other territories. Revascularization as first-line treatment consists of percutaneous transluminal dilatation; surgery must be reserved to difficult cases, such as arterial obliteration or failed dilatation.