Postoperative ileus is a recognized complication of lower extremity surgery. In a review of 21,589 patients who underwent either total hip or total knee arthroplasty between 1988 and 1997, 0.32% developed postoperative ileus. The ileus lasted >3 days in 46% of patients. The purpose of this study was to investigate the risk factors associated with ileus during 3 days after total joint arthroplasty. The average age of the patients with prolonged ileus was 69.1 years, and 70% were male. The development of a prolonged ileus was associated significantly with younger age (P<.005) and male gender (P<.02). In total knee arthroplasty, more cases of postoperative ileus were seen in bilateral surgery. Patients who are younger, male, and undergoing bilateral total knee arthroplasty are at an increased risk of having a more prolonged postoperative ileus and should be monitored closely.