BACKGROUND The effects of infliximab, a tumor necrosis factor-alpha (TNF-alpha) antibody, have been well established in adult patients with inflammatory and fistulizing Crohn's disease. This study evaluates short- and long-term efficacy of infliximab in children with ulcerative colitis. METHODS All pediatric patients with ulcerative colitis who received infliximab between July 2001 and November 2003 at the Johns Hopkins Children's Center were identified. Short- and long-term outcomes and adverse reactions were evaluated. RESULTS Twelve pediatric patients with ulcerative colitis received infliximab for treatment of fulminant colitis (3 patients), acute exacerbation of colitis (3), steroid-dependent colitis (5), and steroid-refractory colitis (1). Nine patients had a complete short-term response, and 3 had partial improvement. The mean per patient dose of corticosteroid after the first infliximab infusion decreased from 45 mg/day at the first infusion to 22.2 mg/day at 4 weeks (P = 0.02) and 7.8 mg/day at 8 weeks (P = 0.008). Eight patients were classified as long-term responders with a median follow-up time of 10.4 months. Of the 4 long-term nonresponders, 3 underwent colectomy, and the fourth has ongoing chronic symptoms. Three of 4 long-term nonresponders were steroid-refractory compared with 1 of 8 long-term responders. Patients receiving 6-mercaptopurine had a better response to infliximab. CONCLUSIONS Infliximab should be considered in the treatment of children with symptoms of acute moderate to severe ulcerative colitis.