Neutralizing alloantibodies (inhibitors) to factor VIII or factor IX develop in approximately 25% of patients with haemophilia A and <3% of patients with haemophilia B treated with factor concentrate. Patients with high titre inhibitors, in whom immune tolerance therapy fails, have few treatment options. Targeted anti-B-cell therapy with rituximab (chimeric anti-CD20) has been useful in several antibody-mediated autoimmune states. Case reports of rituximab treatment in small numbers of haemophilia patients with inhibitors have been inconclusive. We describe three adolescent patients with severe haemophilia and inhibitors treated with four weekly doses of rituximab, 375 mg m−2. Treatment with rituximab was effective in reducing the inhibitor titre in two of three patients. Rituximab may be beneficial for patients with severe haemophilia and inhibitors in whom standard therapies have failed, but larger prospective studies are required to determine safety, efficacy and predictors of success.