We report the case of a 24-year-old woman with systemic lupus erythematosus (SLE). The patient presented with cervical erythema and multiple arthralgia in December, 1996. Based on the high level of antinuclear antibody and the positivity for anti-double-stranded-DNA antibody, we diagnosed the patient as having SLE. Her symptoms improved and her condition was maintained following steroid treatment. In August 2000, the patient suddenly had headache, nausea, vertigo, cerebellar ataxia, fixation nystagmus, and intention tremor. She was negative for the anti-phospholipid antibody. The cerebrospinal fluid IgG index and the IL-6 level were high. MRI of the right cerebellar hemisphere showed an equal-signal-intensity region in the T 1-enhanced image, and a high-signal-intensity region with a diffuse undefined border in the T 2-enhanced image. The increased cerebral blood flow at the site corresponding to a cerebellar lesion detected by magnetic resonance imaging (MRI) was observed by brain single photon emission computed tomography (SPECT). The central nervous system (CNS) lupus was confirmed by the presence of a lesion in the cerebellum. The abnormalities detected in MRI and SPECT images of the brain disappeared immediately after the steroid pulse therapy, and symptoms such as ataxic gait were improved. This patient was diagnosed as having acute neuropsychiatric SLE with cerebellar symptoms that are rarely observed as a localized neural sign of SLE. The MRI and SPECT images suggested the presence of an inflammatory edematous lesion that was confined in the cerebellar hemisphere. This is considered to be due to the increase of vasopermeability.