Despite the advantages offered by laparoscopy in bariatric surgery, the incidence of a new complication that was uncommon in the previous era of open surgery–internal hernias–has increased. Most publications in the literature dealing with internal hernia describe the incidence and form of presentation of this entity but few explain how these complications can be prevented. In this review article we describe a technique to close mesenteric defects in retrocolic Roux-en-Y laparoscopic gastric bypass with permanent, continuous running suture (ethibond). We also review the literature in MEDLINE (www.ncbi.nlm.nih.gov/entrez/ using the key words: obesity, laparoscopy, gastric bypass, internal hernia, Petersen hernia) and references from articles of interest to determine the real incidence of this complication. Our technique has proven to be safe, reliable and reproducible and has greatly diminished the incidence of internal hernias. However, our data need to be analyzed in the future to determine whether the technique described eliminates this complication. The optimal results achieved with complete closure of all mesenteric defects have also been observed by other authors.