Haemophilia is a rare, inherited blood disorder in which blood clotting is impaired such that patients suffer from excessive internal and external bleeding. At present there is no cure for haemophilia A and patients require expensive, life-long treatment involving clotting factor replacement therapy. Treatment costs are perceived to be higher for patients who have developed inhibitory antibodies to factor VIII, the standard therapy for haemophilia A. However, initial cost analyses suggest that clotting factor therapy with alternative haemostatic agents, such as recombinant activated factor VII or activated prothrombin complex concentrate, is no more expensive for the majority of haemophilia A patients with inhibitors than for those without inhibitors. With the availability of effective alternative haemostatic agents, orthopaedic surgery for haemophilia A patients with inhibitors is now a clinical option, and initial cost analyses suggest this may be a cost-effective treatment strategy for patients with inhibitors whose quality of life (QoL) is severely impaired by joint arthropathy. In an era of finite healthcare resourcing it is important to determine whether new treatments justify higher unit costs compared with standard therapies and whether such higher costs are justified from an individual perspective in terms of improved QoL, and from a societal perspective in terms of improved productivity and reduced overall healthcare costs. This paper examines current data on the health economics of treating haemophilia A patients with inhibitors, focusing on the overall costs of clotting factor replacement therapy and the cost consequences of joint replacement.