Trocar injury is one of the most serious and potentially preventable complications of laparoscopic surgery. Use of a blunt rather than a cutting trocar could be expected to lessen the likelihood of this injury. Therefore complications related to laparoscopic port design were studied by comparing conventional cutting trocars with radially expanding (blunt) trocars. A multicenter, prospective, randomized clinical trial was conducted in 250 adult patients undergoing elective laparoscopic procedures at tertiary care centers and community hospitals. The patients were randomly assigned to one of two groups: group C, conventional cutting trocars; or group S, radially expanding trocars. Sixteen surgeons performed 244 elective laparoscopic procedures; six patients were removed from the study. One hundred nineteen patients were assigned to group S and 125 to group C. The groups were similar with regard to age, sex, and type of procedure. The following data were collected: intraoperative complications related to the trocars, abdominal wall bleeding, visceral or vascular injury, other complications, fascial closure, procedure time, trocar site assessment at 4 and 24 hours postoperatively, and visual analog pain scores at 4, 8, 12, and 24 hours postoperatively. Fascial defects from 10 mm or larger trocars in group C were closed; the fascial defects in group S were not closed. The trocar sites were checked for incisional hernias at late follow-up. Mean operating time was not different between the two groups (group S, 92 +/- 73 minutes; group C, 100 +/- 74 minutes). There were no episodes of intraoperative cannula site bleeding in group S compared with 16 episodes in 13 patients (P < 0.001) in group C. Postoperative wound complications were fewer in group S (13 vs. 23; P < 0.05). Although the pain scores were generally lower in group S, the differences were not significant. Only 3% of the patients in group S had fascial defects of 10 mm or greater that had to be closed. Within a follow-up period of 6 to 18 months, there have been no incisional hernias in either group. This study shows that radially expanding trocars are safe and effective, and less likely than conventional trocars to result in intraoperative or postoperative complications. The defects created by the radially expanding trocars do not have to be routinely closed.