We reported a case of intracranial primary malignant lymphoma following Behçet disease treated with colchicine. A 43-year-old female with a past history of oral ulcer and folliculitis visited the Department of Ophthalmology on December, 1990, because of her impaired visual acuity. A diagnosis of uveitis due to incomplete type Behçet disease was made from funduscopic examination and her past history. She had been received 1.0mg/day colchicine for six months in the outpatient clinic. She was referred to our department on August 19, 1991, with nausea and headache. On admission, neurological examination revealed slight right cerebellar ataxia showing dysmetria and dysdiadochokinesis. Computed tomography scan and magnetic resonance images demonstrated a malignant lymphoma in the left cerebellar hemisphere. Stereotaxic biopsy resulted in the B cell type malignant lymphoma (Diffuse large cell type). Galliumscintigraphy, physical examination and peripheral blood examination disclosed no systemic abnormalities. There was a reduction of lymphocyte's response to PHA (phytohemagglutinin) stimulation (1.24). The tuberculin reaction was negative. Colchicine was discontinued and the therapy with radiation and prednisolone (20 mg/day) was started under the diagnosis of intracranial primary malignant lymphoma. She was discharged without any neurological deficits on November 25, 1991. She still suffers from impaired visual acuity, but has no problems in daily life. To our knowledge no intracranial primary malignant lymphoma following Behçet disease has been reported previously. The relationship between Behçet disease treated with colchicine and the occurrence of malignant lymphoma is discussed. In our case we speculated that malignant lymphoma might have occurred in an immunosuppressive state due to administration colchicine.