We describe a patient with metronidazole-induced encephalopathy involving reversible lesions in the anterior commissure, basal ganglia, and cerebellar white matter, which have not been reported previously. We observed inferior olivary hypertrophy, believed to be the result of lesions in the midbrain and cerebellar white matter rather than the result of lesions induced by metronidazole therapy. By using diffusion-weighted imaging and apparent diffusion coefficient maps, we found that metronidazole-induced encephalopathy might be caused by cytotoxic edema.