Behçet's disease is a multi-systemic vasculitis which is characterized by recurrent oral and genital ulceration with positive pathergy test. These features may also be seen in various hematological malignancies. In patients with leukemia who present with Behçet's disease-like features, it is often difficult to ascertain whether the clinical manifestations are due to leukemia, or there is co-existing Behçet's disease too. The authors report an Indian farmer who presented with clinical features suggestive of Behçet's disease with profound neutropenia. On bone marrow examination he was found to have acute monocytic leukemia (AML-M5). Chemotherapy for leukemia did not relieve his oral and genital ulcers, for which glucocorticoids and colchicine had to be given. So the patient had co-existence of Behçet's disease along with AML-M5, which has never been reported in the literature before.