This study evaluates the effect of renal artery stenting on renal function in 72 consecutive patients. Baseline renal function was considered abnormal if creatinine was greater than or equal to 1.5 mg/dl. Improvement was defined as decrease in creatinine by greater than or equal to 20%, unchanged if variation was less than or equal to 20%, and worse if creatinine increased by greater than or equal to 20%. Two patients (2/72 = 2.8%) had in-hospital death. Follow-up creatinine was available in 61/70 (87%) patients at 21 +/- 11 months (9 patients lost to follow-up). Forty-four (44/61, 72%) patients had normal baseline creatinine that remained unchanged in 42/44 (95%, p = ns). Seventeen (17/61, 28%) patients had abnormal baseline creatinine. The renal function improved in 3/17 (18%), from 2.7 +/- 1 to 1.6 +/- 0.6 mg/dl (p = 0.06). Creatinine remained unchanged in 9/17 (53%), and was worse in 5/17 (29%, 2.0 +/- 0.51 to 3.3 +/- 0.34 mg/dl, p = 0.005). In conclusion, the renal function remained stable in 89% of patients and worsened in 11% of patients at 21 months (follow-up available in 87% of the eligible patients) following renal artery stenting. In patients with baseline renal insufficiency (serum creatinine > 1.5 mg/dl), the renal function remained stable in 71% of patients.