A 4-year-old girl developed progressive obtundation following an upper respiratory tract illness. Physical, cerebrospinal fluid, computed tomographic, electroencephalographic, and evoked response findings were compatible with disseminated encephalomyelitis. Skin lesions indicative of incontinentia pigmenti were confirmed by biopsy. Transient loss of suppressor T cells was observed. Prior history revealed that at 6 months of age a similar episode of acute central nervous system deterioration had occurred. Recurrent encephalomyelitis does occur with incontinentia pigmenti. Transient loss of suppressor T cells suggests that this is an immune-mediated process.