Renal artery stenosis is the most common surgically or interventionally curable cause of hypertension. Screening and diagnostic tests are still needed to establish the presence of renal artery stenosis. The aim of our study was to evaluate sensitivity, specificity and diagnostical accuracy of renal artery duplex scanning for diagnosis of renal artery stenosis in hypertensive patients. Between January 2, 1988 and December 31, 1989 we performed renal artery duplex scanning in 128 hypertensive patients in whom were present clinical data suggestive of renal artery stenosis. Angiographic evaluation was performed within 3 months in 23 patients with a positive duplex, and in 15 patients with a negative duplex but highly suggestive for renal artery stenosis clinical data. Studies were performed with an Ultramark 8 duplex scanner (ATL). Data of this report are relative to the analyses performed of 76 renal arteries. Duplex scanning had a sensitivity of 90% and specificity of 96% to detect renal artery stenosis. Diagnostic accuracy was 93% for 50% to 60% stenosis and 100% for occlusion or 60% to 99% renal artery stenosis. Duplex scanning for diagnosis of renal artery stenosis shows agreement with angiography. Duplex scanning, which can distinguish high grade stenosis from occlusion, is able to select patients for possible percutaneous transluminal angioplasty before angiography, and we consider duplex scanning a valid, noninvasive screening or diagnostic test for renovascular hypertension.