BACKGROUND Obstructive sleep apnea is a common condition in patients undergoing bariatric surgery. The aim of this study was to determine the clinical outcome of a cohort of morbidly obese patients with documented sleep apnea who underwent laparoscopic Roux-en-Y gastric bypass (LRYGBP). METHODS 56 morbidly obese patients with documented sleep apnea by polysomnography underwent LRYGBP. There were 36 females with mean age 46 years and mean BMI 49 kg/m2. The Epworth sleepiness scale (ESS) scores and the number of patients requiring the use of continuous positive airway pressure (CPAP) therapy were recorded preoperatively and at 3-month intervals. RESULTS The mean length of sleep apnea condition was 44 +/- 55 months. Preoperative polysomnography scores were classified as severe in 50% of patients, moderate in 30%, and mild in 20%. 29 of 56 (52%) patients required CPAP therapy preoperatively. The mean excess body weight loss was 73 +/- 3% at 12 months. The mean ESS score decreased from 13.7 preoperatively to 5.3 at 1 month postoperatively (P<0.05) and maintained below the threshold level (<7) for the entire 12 months of follow-up. Of the 29 patients requiring preoperative CPAP, only 4 (14%) patients required CPAP at 3 months postoperatively and none required CPAP at 9 months. CONCLUSIONS Weight loss associated with LRYGBP significantly improves the symptoms of sleep apnea and is effective in discontinuation in the clinical use of CPAP therapy. Improvement of obstructive sleep apnea symptoms occur as early as 1 month postoperatively.