A case is reported of early infantile autism associated with a congenital cytomegalovirus infection. The diagnosis of autism is based on the child's failure to develop good interpersonal relationships, poor eye contact, delayed and deviant use of language, and her rote and nonthematic use of objects and playthings. Resistance to change and self-stimulatory behavior were also present. Onset was before 2 years of age. Congenital cytomegalovirus infection was suggested by the presence of an antibody response to the virus, culture of the virus from the urine, sensorineural hearing loss, and inflammatory damage to the retina of the eye. Although over time improvement was noted, at last examination at the age of 5 years her behavior is still markedly deviant. This and other reported cases suggest that congenital viral infection may be an important cause of infantile autism. It is hypothesized that an ability of the agent to establish chronic infection may predispose to behavioral aberration.