BACKGROUND: Infliximab has been shown to be efficacious in acute exacerbations of ulcerative colitis (UC). AIM: To evaluate the cost-effectiveness of infliximab treatment in patients hospitalised with acute exacerbations of UC. METHODS: A decision analysis model was constructed to simulate the progression of acute UC patients treated with infliximab induction regimen over 1 year. Infliximab treatment was compared with standard care, ciclosporin and surgery using transitions derived from infliximab and ciclosporin randomised trials. Costs and outcomes were discounted at 3.5%. Intermediate outcomes of colectomy and post-surgery complications were translated into the primary effectiveness measurement, which was quality-adjusted life years (QALYs) estimated using EQ-5D. One-way and probabilistic sensitivity analyses were performed to estimate the uncertainty around the results. RESULTS: The incremental cost effectiveness ratio (ICER) for infliximab was pound19,545 per QALY compared to ciclosporin, which in turn dominated standard care. Sensitivity analysis indicated patient body weight, utility estimates and treatment effect of alternative treatment strategies to be the most important factors affecting cost-effectiveness. CONCLUSION: Infliximab induction regimen appears to be a cost-effective treatment option for UC patients hospitalised with an acute exacerbation.