The reported overall incidence of postoperative Small Bowel Obstruction (SBO) is 0.69 per cent. This study examined the incidence and risk factors for early postoperative SBO for penetrating abdominal trauma (PAT), with early SBO defined as SBO within 6 months of operation. This was a prospective cohort study of patients admitted to a Level 1 Trauma Center from 5/91 to 12/93 who required celiotomy for PAT. Patients were followed at least 6 months for readmission for SBO to be considered evaluable. Of 341 patients undergoing celiotomy for PAT and surviving to discharge, 298 (87.4%) were evaluable. The overall incidence of early SBO was 7.4 per cent and varied between 2.3 per cent (nontherapeutic celiotomy) and 10.8 per cent (small/large bowel injury). All patients with celiotomy for PAT are at increased risk for early SBO compared with elective surgery patients. Those with small/large bowel penetration or gunshot wounds are at the highest risk. Previous abdominal surgery is not a risk factor for early SBO in PAT patients. Surgeons and Managed Care case managers should devote special attention to close follow-up in PAT patients, particularly those with the risk factors identified in this study.