BACKGROUND Hyperlipidemia is an established risk factor for development of coronary artery disease. The aim of our study was to examine the changes in serum lipid profiles of morbidly obese patients complicated by hyperlipidemia, who underwent laparoscopic gastric bypass. METHODS We retrospectively reviewed the charts of 95 morbidly obese patients with documented hyperlipidemia who underwent laparoscopic gastric bypass. Mean duration of hyperlipidemia was 44+/- 56 months. Hyperlipidemia was defined as an elevated level of triglycerides (> 150 mg/dL) or total cholesterol (> 200 mg/dL). Changes in lipid profile of a subset of patients with subnormal levels of high-density lipoprotein cholesterol (<or= 40 mg/dL), high levels of low-density lipoprotein cholesterol (> 130 mg/dL), and very-low-density lipoprotein cholesterol (> 40 mg/dL) were also examined. Fasting lipid profiles were measured preoperatively and at 3-month intervals. RESULTS There were 68 women (72%) with a mean age of 43 +/- 10 years. Mean body mass index was 47+/- 5 kg/m2. Mean percentage of excess body weight loss at 12 months postoperatively was 66%. One year after gastric bypass, mean total cholesterol levels decreased by 16%; triglyceride levels decreased by 63%; low-density lipoprotein cholesterol levels decreased by 31%; very-low-density lipoprotein cholesterol decreased by 74%; total cholesterol/high-density lipoprotein cholesterol risk ratio decreased by 60%, and high-density lipoprotein cholesterol levels increased by 39%. Also, within 1 year, 23 of 28 (82%) patients requiring lipid-lowering medications preoperatively were able to discontinue their medications. CONCLUSIONS Weight loss after laparoscopic gastric bypass substantially improves lipid profiles in morbidly obese patients who have hyperlipidemia. Improvement in lipid profiles was observed as early as 3 months postoperatively and was sustained at 1 year. Improvement of lipid profiles after laparoscopic gastric bypass can reduce health risks associated with high levels of atherogenic lipoproteins.