The diagnosis and successful treatment of a cerebral aneurysm in a 1-month-old child are described. A review of the few aneurysms previously recorded in children up to three months of age reveals that such aneurysms tend to be large, but show no predilection for any particular site, although a relatively large number of them arise from the vertebrobasilar circulation. They occur more commonly in females and are usually congenital. Surgery has been undertaken successfully in about one-third of the cases.