OBJECTIVE: To evaluate whether body mass index (BMI) has an impact on the outcomes of tubeless percutaneous nephrolithotomy (PCNL). PATIENTS AND METHODS: We retrospectively reviewed patients who underwent tubeless PCNL at our institution from 2006 to 2011. Specifically, stone-free rates, complications, and hospital length of stay (LOS) were assessed. Patients were divided into four groups based on BMI: <25, 25-29.9, 30-34.9 and ≥35 kg/m(2) . Baseline characteristics and outcomes were compared between BMI groups. Multivariable logistic regressions were used to evaluate the independent contribution of BMI as a predictor of outcomes. RESULTS: We identified 268 patients who fulfilled study requirements. The overall stone-free and complication rates were 52.5% and 19.0%, respectively. Minor and severe complication comprised 10.4% and 8.6%, respectively. Univariate and multivariable analyses showed no association between BMI and stone-free or complication rates. However, patients with a normal BMI had significantly higher transfusion rates (P = 0.005), and were significantly more likely to have a prolonged LOS (≥2 days), when compared with an overweight BMI (P = 0.032) CONCLUSIONS: BMI did not impact the stone-free, or complication rates of tubeless PCNL. Normal BMI was found to be a risk factor for prolonged LOS, which may be due to an increase in clinically significant bleeding in this patient population. Tubeless PCNL appears to be a safe and effective procedure for the treatment of complex renal calculi, independent of BMI.