Objective To assess the incidence of local infection when multifilament braided and monofilament permanent suture materials were passed, full thickness, through the vaginal wall. Methods A retrospective review was performed with 110 women who had a modified long needle suspension procedure for stress urinary incontinence in which permanent suture material was passed, full thickness, through the vaginal mucosa. In the initial 41 cases, silicone-coated, braided polyethylene sutures were used. Monofilament polypropylene was used in 69 cases. Suture infection was evaluated by review of clinic records and by telephone interview of all patients. Results The incidence of suture infection with braided polyethylene suture and monofilament polypropylene suture groups was 24.6% and 0%, respectively. Conclusions Vaginal exposure to silicone-coated, braided polyethylene sutures produces a significant incidence of local infection, whereas vaginal exposure to polypropylene sutures does not. A review of the literature concerning bacterial infections of various suture materials indicates that the physical properties of the suture may explain this observation. © 1998 Lippincott Williams & Wilkins, Inc.