Our study aimed to evaluate the effect of preservation or elective division of the ilioinguinal nerve on pain and postoperative symptoms after open inguinal hernia repair with mesh. Double-blind, randomized trial. Four public, government-financed hospitals in Italy. From January 1, 1997, to June 30, 2002, 813 patients with primary inguinal hernia were randomly allocated to undergo inguinal hernia repair either with ilioinguinal nerve preservation (408 patients, group A) or elective transection (405 patients, group B). Hernia repair with sutureless apposition of a polypropylene mesh. The primary outcome was the evaluation of chronic pain 1 year after operation. Secondary outcomes were postoperative symptoms assessment at 1 week and 1, 6, and 12 months after operation. Telephone interview was performed 35.5 months (range, 12-59 months) after operation to assess the presence of chronic pain. Of the 302 group A and 291 group B patients who made an office visit 1 year postoperatively, pain was absent in 231 (76.5%) and 213 (73%) (difference, 3.30%; 95% confidence interval, -3.68% to 10.28%), mild in 55 (18%) and 60 (21%), moderate in 11 (4%) and 9 (3%), and severe in 5 (2%) and 9 (3%), respectively (P =.55; Pearson chi2(3) test). At 1-month and 6-month follow-up visits, no difference was found between the 2 groups with respect to pain, but loss of pain or touch sensation were significantly greater when the ilioinguinal nerve was divided. One year after operation, the 2 groups were also comparable with respect to loss of pain sensation, but touch sensation remained decreased in group B. At telephone interview, the presence of chronic pain was similar in both groups. Pain after open hernia repair with polypropylene mesh is not affected by elective division of the ilioinguinal nerve; sensory disturbances in the area of distribution of the transected nerve are significantly increased.