A prospective study of patients with ventral hernias was undertaken to study the experience with an open intraperitoneal underlay technique utilizing a bilayer prosthetic mesh. From September 1998 to March 2001, 102 patients underwent repair with a bilayer expanded polytetrafluoroethylene (ePTFE) and polypropylene mesh placed intraperitoneally and fixed in place with full-thickness abdominal muscle wall sutures to achieve a 5-cm underlay of the fascial defect circumferentially. There were 67 females and 35 males ranging in age from 29 to 76 years (mean 53 years). Average patient weight was 207 lb with 64 patients in the obese category. Forty patients presented with recurrent hernias. Mean operative time was 103 minutes with an average diameter hernia defect size of 15 cm. Median hospital stay was 3 days. There was no surgical mortality, and major morbidity occurred in six patients (2 wound infections, one deep vein thrombosis, one myocardial infarction, one pneumonia, and one pulmonary embolus). Mean follow-up is 28 months (range 12-42 months). No recurrence has been found with 100 per cent follow-up to date. No bowel obstruction or enteric fistulas have occurred during the follow-up period. The open intraperitoneal underlay mesh technique can be performed with a zero per cent early recurrence rate. Bilayer prosthetic mesh composed of ePTFE and polypropylene can be safely placed intraperitoneally without causing intestinal obstruction or enteric fistula.