BACKGROUND: Ventral hernia is a common complication of open Roux-en-Y gastric bypass (RYGB). The aim of this study was to determine whether prophylactic mesh placement during RYGB would reduce the incidence of postoperative hernias. METHODS: Obese patients undergoing RYGB by a single surgeon had prosthetic mesh placed in a subfascial location at the conclusion of the procedure. The incidences of recurrent hernia and morbidity associated with the placement of mesh were assessed. RESULTS: Sixteen patients underwent RYGB with prophylactic mesh placement over 6 months. The average preoperative body mass index was 46.6 kg/m(2). Half of the patients were diabetics. None were smokers. During mean follow-up of 6 months, 4 patients (25%) required mesh excision, 3 for infection and 1 for a persistently symptomatic seroma. One patient was explanted incidentally in the course of reexploration for intractable nausea and vomiting. Another developed an incisional hernia despite prophylactic mesh. CONCLUSIONS: In the investigators' experience, the use of prophylactic new-generation mesh at the time of open RYGB led to an unacceptable rate of local complications. They caution against this technique in patients undergoing open RYGB.