This paper reports a systematic review of the cost-effectiveness of treatment options in patients with haemophilia A with inhibitors. As very little relevant published evidence was identified, an economic modelling exercise was undertaken to calculate the cost-effectiveness of different strategies in the treatment of high-responding haemophilia A patients with inhibitors. A decision analysis approach was used to model the expected lifetime clinical outcomes and costs of the more common regimens currently used in UK in treating severe haemophiliacs with inhibitors. The model attempts to reflect the outcomes of clinical events, costs and life expectancy for each different treatment regimen for haemophilic boys with inhibitors who are high responders (defined as inhibitor level >/=10 BU) throughout their life. The basic model structure is centred on a Markov decision process, which was used to simulate, at quarter-yearly intervals, the movement through discrete health states and their complications. The model allows a comparison of cost-effectiveness between three immune tolerance induction (ITI) regimens (Bonn, Mälmo and Low-Dose protocols) and against a relevant 'on-demand' (OD) regimen. It also shows the cost-effectiveness of different OD regimens using different bypassing agents. The results of the economic modelling indicate that treating haemophilia A patients who have high-responding inhibitors OD with recombinant activated factor VII is cost-effective compared to treatment with activated prothrombin complex concentrates. However, when OD treatment regimens are compared with the three ITI protocols, the Malmö ITI protocol is the preferred treatment strategy, generating more quality adjusted life-years (QALYs) and less cost than either an OD regimen or the Bonn or Low-Dose ITI protocols.