Purpose: Factors predicting renal function and recurrent stenosis following percutaneous renal revascularization are poorly identified. The predictive value of hemodynamic duplex ultrasound (DUS) parameters was evaluated. Methods: In a prospective observational study patients undergoing stenting of renal artery stenosis (RAS) were included. Renal resistance index (RI) and peak systolic velocity (PSV) were measured at baseline, one day, and six months after intervention. Results: At 6-months follow-up 16 (16.8%) restenosis of 105 treated renal arteries were detected. Baseline RI was 0.69 +/- 0.12 and increased significantly to 0.72 +/- 0.09 after 6 months (p < 0.0001), however, RI did not predict restenosis. PSV at baseline and age were independent predictors for increased RI at 6 months (p = 0.0078 and p = 0.0019). Diabetics had a significant higher RI before revascularization (0.74 +/- 0.08) than non-diabetics (0.68 +/- 0.12, p = 0.04). PSV after stenting was higher in patients with restenosis (1.4 +/- 0.4 m/sec vs. 1.0 +/- 0.3 m/sec, p = 0.002) and was an independent predictor for restenosis. Conclusions: Increased PSV within the stent one day after the procedure is predictive for restenosis. Patients with high grade RAS and older patients have a worse outcome. DUS is recommended to detect patients at risk for restenosis after percutaneous renal revascularization.