Background. Medical management of moderate to severe Crohn's disease (CD) using immunomodulator agents has not eliminated surgical treatment of disease complications. The effect of improved medical treatment on perioperative CD surgical outcome is not known. We analyzed the impact of immunomodulator therapy on the rate of intraabdominal septic complications (IASC) in CD patients undergoing bowel reanastomosis or strictureplasty. Methods. Surgical outcome was reviewed in 100 consecutive CD patients who underwent segmental resection with primary anastomosis or strictureplasty between 1998 and 2002. Multivariate analysis was performed to determine the effect of immunomodulator therapy on rate of IASC (intraabdominal abscess, anastomotic leak, or enterocutaneous fistulae). Immunomodulator agents included azathioprine, 6-MP, methotrexate, and infliximab. Results. IASC developed in 11 of 100 (11%) operations. Immunomodulator use was associated with fewer IASC (4/72 procedures; 5.6%), compared with 7/28 (25%) cases with patients not on therapy (P < .01). IASC were not influenced by steroid use, smoking status, preoperative abscess, or fistula or albumin levels. Immunomodulator use did not affect the length of resection or the rate and number of strictureplasties. Conclusion. Medical management with immunomodulator therapy is safe and significantly decreases postoperative IASC in CD patients undergoing surgical procedures requiring bowel anastomosis or strictureplasty.