A 59-year-old Japanese woman, diagnosed with mixed connective tissue disease (MCTD) and chronic myelogenous leukemia (CML), developed several characteristic features of Behçet's disease (BD) after receiving alpha-interferon (IFN-alpha). She displayed recurrent oral aphtha, genital ulceration, erythema nodosum at the bilateral arm, and low grade fever. The skin of the femur where the IFN-alpha was injected showed modular acneiform changes. Skin biopsy revealed perivascular infiltration. The symptoms compatible with BD improved after discontinuation of IFN-alpha and the introduction of prednisolone and azathioprine. This is the first description of BD induced by IFN-alpha.