Objectives: Laparoscopic nephrectomy in patients with known venous involvement is an emerging technique. The goal of this study was to describe our experience and outcomes with laparoscopic nephrectomy for patients with preoperatively diagnosed level I (renal vein) tumor thrombus. Methods: The data from all patients undergoing laparoscopic nephrectomy by one surgeon from July 1, 2004 to February 28, 2006 were reviewed. The patients with a preoperatively diagnosed tumor thrombus were included in the study. A pure laparoscopic transperitoneal technique was used with intraoperative ultrasonography to ensure complete removal of the thrombus. The medical records were reviewed for clinical, operative, and follow-up information. Results: Five patients were identified. The mean age, American Society of Anesthesiologists score, and tumor size were 59.8 years (range 34 to 81), 2.6 (range 2 to 3), and 5.5 cm (range 4 to 6), respectively. The mean operative time and estimated blood loss were 119.6 minutes (range 92 to 180) and 150 mL (range 50 to 300), respectively. The mean hospital stay was 3.6 days (range 2 to 4), and no complications occurred. The final stage was T3b with negative margins in all cases. The mean Fuhrman grade was 2.4 (range 2 to 3). Two patients had known metastases and underwent cytoreductive nephrectomy. These 2 patients were alive at a mean follow-up of 11.5 months. Of the other 3 patients, at a mean follow-up of 8.7 months, 2 had no evidence of disease, and 1 had developed recurrence in the liver and was treated with sorafenib, resulting in tumor regression. Conclusions: Pure laparoscopic transperitoneal nephrectomy for patients with preoperatively diagnosed level I tumor thrombus is safe and effective in experienced hands. Additional series are needed to examine the long-term oncologic outcomes.