Objectives: Laparoscopic adrenalectomy has become an effective option for aldosteronoma. We evaluated the retroperitoneal approach with regard to safety, efficacy, invasiveness and cost-benefit ratio in patients with primary aldosteronism. Methods: Between July 1999 and June 2005, we carried out a total of 195 retroperitoneoscopic adrenalectomies (RA) in one hospital, including 108 on the left and 87 on the right, in 78 men and 113 women aged 20-78 years (mean age 48.2 years) with aldosteronoma. Average adrenal tumor size was 16 mm (range 10-32 mm). The 195 operations were divided into 10 groups of 20 operations each, and the mean duration and estimated blood loss for each group were compared. Results: The mean operating time and intraoperative blood loss in RA were 93.2 Ϯ 37.4 (45-210) min and 68.5 Ϯ 53.2 (5-210) mL, respectively. Compared to group 1 (cases 1-20), a statistically significant decrease in operative time and estimated blood loss were seen in and after group 4 (Ն case 61, 94.5 Ϯ 30.3 vs 139.2 Ϯ 44.7 min, P < 0.01), and in and after group 5 (Ն case 81, 67.5 Ϯ 50.5 vs 120.5 Ϯ 60.9 mL, P < 0.01), respectively. No differences were found in duration of surgery and estimated blood loss between left and right sided tumors (P > 0.05). The mean postoperative hospital stay was 4.5 Ϯ 1.2 days. Postoperative complications, including hematoma and wound infection, occurred in 4.1% of patients. Conclusions: Retroperitoneoscopic adrenalectomy for aldosteronoma is a safe, effective, and minimally invasive approach with an advantageous cost-benefit ratio. With accumulated experience, it can expedite the learning curve for RA.