Tension-free inguinal hernia repair is one of the so-called painless operations. Mild or medium postoperative pain, however, even in the mesh repair era, is common and usually due to ilioinguinal nerve entrapment or mesh fixation in the periostium of the pubic tubercle. Especially in indirect inguinal hernia repair, however, hernia sac ligation and excision may be the cause of pain. The aim of this study was to conduct a single-center prospective randomized trial with a view to clarify this issue on a scientific basis. In an 8-year period, all patients undergoing elective indirect inguinal hernia repair using a tension-free polypropylene mesh technique were randomized to induce high hernia sac ligation or not in a double blind manner. The main endpoint was to detect any difference in postoperative pain between the two groups. Between January 1999 and December 2006, 477 patients with indirect inguinal hernia entered the study and were randomized to have high hernia sac ligation and excision (group A, n = 238) or not (group B, n = 239). The two groups were comparable regarding demographic data. Postoperative pain was associated with statistically significantly more episodes in group 1, 27% (65/238), than in group 2, 10% (24/239), on day 1, 9% (22/238), compared to 3% (8/239) on day 7, 2% (5/238), compared to 0% (0/239), on day 30, respectively, and these results were statistically significant (P <or= 0.05). All patients were treated conservatively. From the results of this study, it appears that we are able to demonstrate a significant benefit from the omission of high hernia sac ligation and excision on postoperative pain in patients who undergo tension-free indirect inguinal hernia mesh repair.