Résumé : Background Weight loss issues are one of the problems that can affect patients after undergoing bariatric surgery. We report the feasibility, safety and preliminary outcomes of laparoscopic conversion of Roux-en-Y gastric bypass (RYGB) to sleeve gastrectomy (SG), as a first step of duodenal switch (DS), for insufficient weight loss or weight regain. Patients and Methods Between August 2007 and November 2009, four patients benefited from laparoscopic conversion for insufficient weight loss or weight regain, mainly due to a new dietary behaviour such as sweet eating. At the time of RYGB, the mean weight and body mass index (BMI) was 118.5±32.8 kg and 43.2±8 kg/m2, respectively. The mean interval time between RYGB and conversion to SG was 36.7±15.6 months. At the time of conversion, the mean weight, BMI, % excess weight loss (%EWL) and % excess BMI loss (%EBMIL) was 101.7±24.7 kg, 37.3± 6.6 kg/m2, 27.5±11.8% and 26.5±12%, respectively. The procedure involved the dismantling of both anastomosis, performance of SG before restoration of gastric continuity, and new small bowel anastomosis. Results Mean operative time was 233.7±46.4 min. There were no conversions to open surgery and no mortality. One patient developed a gastric fistula. Mean hospital stay was 20.2±17.9 days. After a mean follow-up of 11± 12.8 months, the mean weight, BMI, %EWL and %EBMIL was 81±12.1 kg, 30.3±5.1 kg/m2, 59.3±31.5% and 42.3± 34.5%, respectively. During follow-up, one patient underwent the second step of DS. Conclusions Laparoscopic conversion of RYGB to SG is feasible and safe despite the development of gastric fistula. Weight loss is increased, leaving the patients in better conditions to undergo the second step of DS. © Springer Science+Business Media, LLC 2010.