OBJECTIVE Our aim was to evaluate the safety and efficacy of percutaneous nephrolithotomy (PCNL) with ultrasonography (US)-guided renal access in the lateral decubitus flank position. METHODS From July 2006 to March 2008, 40 patients with renal stones > 2 cm underwent PCNL with US-guided renal access in the lateral decubitus flank position by a single surgeon. We report our technique and the outcomes in detail. RESULTS Successful access was achieved in 40 patients (100%). Complete stone clearance rate was 85% (34 patients). After surgery, six (15%) patients had stones (6-11 mm) detected by plain abdominal radiography or sonography and were referred for shockwave lithotripsy. The mean stone size was 29 mm (range 22-43 mm). The mean operative time was 45 minutes (range 32-75 min), and the mean hospital stay was 2.8 days (range 2-4 d). Postoperative US did not reveal considerable fluid collection. There were no visceral injuries. Also, there was no significant bleeding that led to transfusion intraoperatively and postoperatively. CONCLUSIONS PCNL with US-guided renal access in the lateral decubitus flank position is safe and convenient, and prevents harmful effects of radiation for the surgeon, the surgical team, and the patient.