Clinical trials have shown the expanded polytetrafluoroethylene (ePTFE) membrane to be a highly effective adhesion barrier in gynaecological reconstructive surgery, but the material has not gained wide acceptance because of uncertainty about long-term safety. We conducted a prospective, observational multicentre study to determine if permanent implantation of the ePTFE membrane in the pelvis caused any adverse effects. The subjects were 146 women in whom the membrane was implanted permanently during peritoneal reconstruction in 1991-1996. Postoperatively, patients were examined at regular intervals. The mean postoperative observation time was 3.5 years. No long-term complications occurred. There were 10 births by Caesarean section and 12 by vaginal delivery. All of the pregnancies before these 22 births were uneventful, including 10 in which the women had uterine implantation sites. There were two ectopic pregnancies and three spontaneous abortions. Since the primary purpose of the study was to evaluate the long-term safety of ePTFE, early second-look laparoscopy was not performed routinely. Nevertheless, 24 women had a subsequent operation. Adhesions were present at 8/21 of the membrane sites in these women, a significant decrease compared with adhesions at 17/21 sites during the initial procedure (P = 0.005). This large, multicentre study confirmed the long-term safety of the ePTFE membrane in pelvic reconstruction. Removal of the barrier is not necessary. [ABSTRACT FROM AUTHOR]