The aim of this study was to compare renal function between patients with renal angiography and patients with renal angiography and angioplasty (AP) for renal artery stenosis (RAS). Forty-seven patients with suspected RAS were prospectively investigated by digital subtraction angiography (DSA) using non-ionic low osmolar contrast media (CM). In 22 patients RAS was detected and in 16 cases an angioplasty was performed in the same session. The following parameters were determined 1 day prior to and after the DSA, respectively: serum creatinine (S-Crea, micromol/l) and single-shot inulin clearance (In-Cl, ml/min) for the evaluation of renal function; and urine alpha 1-microglobuline (AMG, microg/g Crea) and beta-N-acetyl-glucoseaminidase (beta-NAG, U/g Crea) as markers of tubular toxicity. Serum creatinine was measured additionally 2 days after CM had been injected. In both groups with and without AP 174+/-65 and 104+/-56 ml of CM ( p<0.0005) were used, respectively. There were no differences with regard to renal function or risk factors for CM nephrotoxicity between both groups. In the group with AP S-Crea and In-Cl (each: mean+/-SD) did not change significantly (before DSA: 171+/-158 and 61+/-24, after DSA: 189+/-177 and 61+/-25, respectively), beta-NAG (median) rose from 4 to 14 ( p<0.05) and AMG from 8 to 55 (n.s., because of high SD). In the group without AP S-Crea increased from 134+/-109 to 141+/-113 ( p<0.01), In-Cl dropped from 65+/-26 to 62+/-26 ( p<0,01), beta NAG (median) rose from 4 to 8 ( p=0.01), and AMG from 7 to 10 (n.s.). A rise in baseline S-Crea by more than 25% or 44 micromol/l occurred in 4 and 2 patients in the group with and without AP, respectively. Creatinine increase was reversible in all cases within 7 days. In this study using sensitive methods to detect changes of renal function and tubular toxicity no additional renal function impairment in DSA with angioplasty for RAS compared with DSA alone could be demonstrated. Our data suggest that AP performed for RAS has a beneficial effect on renal function.