This study reports the clinical benefit and safety of the murine chimeric anti-tumor necrosis factor (TNF)-alpha monoclonal antibody, infliximab, in the treatment of patients who developed findings compatible with Crohn's disease after undergoing colectomy with ileal-pouch anal anastomosis (IPAA) for an original diagnosis of ulcerative colitis. Medical records of 7 patients with Crohn's disease and an IPAA treated with infliximab were reviewed. Clinical response was classified as complete response, partial response, and no response. Concurrent treatment with immune modifier agents and/or antibiotics was recorded. Seven patients with active inflammatory or fistulizing Crohn's disease and an IPAA performed for diagnosis of ulcerative colitis were treated with infliximab after they had no response to conventional therapies. Patients received 1-4 infliximab infusions at a dose of 5 mg/kg. All patients improved clinically. Six patients had a complete response, and 1 had a partial response. Four of the 5 patients with complex perianal and fistulizing disease had closure of all fistula tracts, and 1 patient improved temporarily. Six of the 7 patients underwent concurrent treatment with immune modifier drugs. One patient had myalgias and malaise after the first infliximab infusion and flu-like symptoms after the second one. No other adverse effects were observed. This case series demonstrates that the murine chimeric anti-TNF-alpha monoclonal antibody, infliximab, can be used successfully to treat patients with Crohn's disease involving an IPAA who are refractory to conventional therapies.