Due to the results of a 6-year experience with civilian penetrating colon injuries at Mount Carmel/Grace Hospital, in Detroit, Michigan, which had favored primary repair of colon injuries, a prospective randomized study was performed. Seventy-one patients with penetrating colon injuries were entered in a prospective randomized study. Forty-three patients were treated with primary repair or resection and anastomosis, and 28 patients were treated with diversion. The average Penetrating Abdominal Trauma Index score was 25.5 for the primary repair and 23.4 for the diversion groups. The majority of injuries as assessed by the Colon Injury Score (CIS) for the primary repair group were grades 2 (58%) and 3 (28%). The diversion group predominantly had grades 2 (64%) and 3 (25%). There was no significant difference between the two groups. There were 8 (19%) patients with colon and noncolon-related complications in the primary repair group, and 10 (36%) patients with colon, noncolon, and colostomy-related complications in the diversion group. In addition, there were 2 (7%) patients with complications following colostomy reversal. Independent risk factors for adverse outcomes were compared and used to calculate the probability for adverse outcomes with respect to the mode of treatment. The probability for adverse outcomes was statistically greater in the diversion group. An analysis was also made within the primary repair group comparing the subgroups of primary repair with, and without, resection of colon. It appears that the primary repair with resection of colon may have fewer complications; however, this conclusion is based on a statistically insufficient sample size. The authors contend that primary repair or resection with anastomosis is the method of choice for treatment of all penetrating colon injuries in the civilian population despite any associated risk factors for adverse outcomes.