Rubella encephalopathy occurred in six children. This complication was estimated to have occurred in a ratio of 1:5,000 cases of rubella infection. Three children survived without sequelae; the other three died. Rubella virus was isolated from the throat of a survivor and from the lung of a child who subsequently died. Specimens had been collected on the sixth and seventh day after onset of rash, respectively. Other clinical and autopsy specimens, including brain, failed to yield virus. Antibodies against the rubella virus were demonstrated in the four cases from which serum was available. Cortisol-production rate was increased in the three patients, who subsequently died, who were treated with hypothermia, and was normal in a surviving patient with a milder case of rubella encephalopathy. Observations at autopsy revealed severe, nonspecific degeneration of the central nervous system but no changes specific for viral infection. The incidence and the clinical, virologic, and autopsy findings of this complication are contrasted with those of measles encephalitis.