Manifestations of dementia occurred in two young patients with disseminated lupus erythematosus who had no signs of focalized neurological deficit. In case 1 followed for 8 years, a probably autonomous and familial psychiatric syndrome was complicated during a lupus flare-up by a prolonged dementia syndrome which regressed to a large extent. In the second patient with moderate dementia and familial hearing loss, severe mental deterioration suddenly occurred with long-term degradation of the cognitive capacity. In both of these cases with neurolupus, the frontal clinical signs, the neuropsychological deficits evidenced at testing, and the lesions demonstrated at CT scan and magnetic resonance imaging favored a frontal and/or frontobasal type dementia. Treatment with cyclophosphamide was effective in case 1 after failure of corticosteroid therapy.