Abstract： Objective To investigate the efficacy of laparoscopic Roux-en-Y gastric bypass (LRYGB)in the treatment for obesity and type 2 diabetes mellitus(DM).Methods Twenty-one cages of obesity and 9 cases of type 2 DM received the LRYGB.Weigh changes,excess body weight lose rate (EWL%)and blood glucose level were measured after surgery and occurrence of complications was observed postoperatively.Results LRYGB procedures in all the 30 cases were successfully performed with no conversion to open surgery.Average operation time was 168 minutes(110-270 mins),volume of blood loss during the surgery was 24.0 ml(10-75 ml).Twenty-one cases of simple obesity received follow-up from 2 months to 5 years.Body weight and BMI decreased significantly in one month[(85.1±10.1)kg vs(97.2±15.0)kg,31.2±2.2 vs 35.3±3.5,both P<0.01]and to a minimal level in 2 to 3 years [(66.8±9.2)kg,24.3±1.1],and then maintained at this level.EWL%was correspondingly higher(all P<0.05).Nine type 2 DM patients were followed up for 3 to 8 months,fasting blood glucose and blood glucose OGTT2 hours decreased significantly[(5.9±1.4)mmol/L vs(12.6±2.6)mmol/L,(7.8±1.4)mmol/L vs(17.8±4.1)mmol/L,both P<0.05],of whom 4 patients with obesity decreased in BMI significantly(P<0.05),and 5 patients without obesity had no significant changes in BMI(P>0.05).Five cases(16.7%) had postoperative complications,including 1 case of death due to acute fulminant pancreatitis,1 case of mesenteric hiatal hernia with obstruction in line for reoperation,and the other 3 cases of healing by conservative therapy.Conclusions Treatment of obesity and type 2 DM by LRYGB surgery is feasible with significant short term result.Long term outcome needs further observation.