Objective To evaluate the safety and efficacy of percutaneous nephrolithotomy (PCNL) with B ultrasound-guided renal access in the lateral decubitus flank position for complex renal calculi. Methods From June 2004 to August 2009, 650 patients with renal stones≥20 mm underwent PCNL with B ultrasound-guided renal access in the lateral decubitus flank position. 512 men and 138 women,with a mean age of 38 years(range 11 - 78 years)and a mean stone size of 31 mm(range 20 - 58 mm). Results Successful access was achieved in 650 patients (100%). Minimally PCNL and PCNL were performed in 493 and 157 patients. Complete stone clearance rate was 86. 6% (563/ 650). The mean operative time was 72 min(range 35 - 145 min), and the mean hospital stay was 18d (range 9 - 32 d). There were no visceral injuries. Conclusions PCNL with B ultrasound-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.