Objectives: To evaluate the safety and feasibility of robotic partial nephrectomy for patients with complex renal masses. Methods: We reviewed the data for 164 consecutive patients who had undergone transperitoneal robotic partial nephrectomy at a tertiary care center from February 2007 to June 2010. Of the 112 patients who had available imaging studies to review, 67 were identified and classified as having a moderately or highly complex renal mass according to the R.E.N.A.L. nephrometry score (≥7) (tumor size - [R]adius, location and depth - [E]xophytic or endophytic; nearness to the renal sinus fat or collecting system [N]; anterior or posterior position [A], and polar vs non-polar location [L]). The preoperative, perioperative, pathologic, and functional outcomes data were analyzed. Results: The median body mass index was 29.6 kg/m2 (range 19.9-44.8). Of the 67 patients, 32 were men and 35 were women, with 32 right-sided masses and 35 left-sided masses. The median tumor size was 3.7 cm (range 1.2-11), and the median operative time was 180 minutes (range 150-180). The median estimated blood loss was 200 mL (range 100-375), and the warm ischemia time was 19.0 minutes (range 15-26). The median hospital stay was 3.0 days (range 3-4). The estimated glomerular filtration rate was calculated at a median decrease of 11.1 mL/min/1.73 m2 (range 9-1.3). According to the Clavien-Dindo classification of surgical complications, 2 grade 1, 12 grade 2, and 1 grade 3 complication occurred. All margins were pathologically negative, except for 1, and, after a mean follow-up of 10 months, no recurrences had developed. Conclusions: Robotic partial nephrectomy is a safe and feasible option for moderately or highly complex renal masses determined by the R.E.N.A.L. nephrometry score. The warm ischemia time, blood loss, and complications were increased with highly complex masses. © 2011 Elsevier Inc.