OBJECTIVES: To evaluate the cost-effectiveness of Infliximab (IFX) treatment in severe, active paediatric ulcerative colitis (pUC) METHODS: A Markov model was constructed based upon the literature, to model the progression of a cohort of pUC patients treated with IFX and ciclosporin (CIC) used off-label in the rescue therapy setting. The transition probabilities were estimated from the IFX phase III trials (T72, ACT1 and ACT2).The comparative efficacy was incorporated by using the odds ratio for IFX vs. CIC from a head to head trial in adults (Laharie et al). Utility weights from observational studies (SOLUTION and Arseneau et al) were assigned to the health states within the Markov process. Incremental cost-effectiveness ratios (ICERs) were estimated with a one year time horizon. Uncertainty around key variables was explored through deterministic sensitivity analysis. RESULTS: Compared to CIC in the rescue therapy setting, IFX was a dominant treatment option (produced more QALYs at a lower cost). The results were sensitive to the number of days patients were hospitalised for each treatment, the comparative rates of adverse events and altering the odds ratio for comparative effectiveness. CONCLUSIONS: IFX is a highly effective and well-tolerated therapy for the treatment of paediatric patients with severely active ulcerative colitis. IFX is the only biologic treatment licensed for this population, and is cost-effective when compared to the commonly used off-licence treatment CIC.