A 50-year-old man presented with neuro-Behçet's disease (NBD) manifesting as a large neoplasm-like lesion affecting the brainstem, basal ganglia, and white matter of the cerebral hemisphere. He had no history of disease except for psychoneurosis. On admission, neurological examination found left hemiparesis and dysarthria. Magnetic resonance (MR) imaging showed multiple small ring-like enhancement in the basal ganglia, brainstem, and deep white matter. Biopsy of the mass was performed. Histological examination revealed invasion of inflammatory cells in the white matter, especially around the blood vessels. After the brain biopsy, the patient developed oral aphthae, genital ulcers, and skin eruptions, which are indicative of Behçet's disease. MR imaging after three courses of steroid pulse therapy revealed that the edematous lesion had become smaller with minimum midline shift. NBD should be considered in the differential diagnosis of lesions with multiple ring-like enhancement extending from the basal ganglia to the brainstem, because dermatological manifestations are sometimes obscured during periods of remission.