Chiefly because of advances in prenatal diagnostic ultrasonography, prognostic data on congenital hydrocephalus have increased in pertinence. Neurosurgeons may be confronted with requests for prognostic information after discovery of gestational hydrocephalus. Because previous reports reflect technical problems, complications, and less favorable results of an evolutionary period in hydrocephalus therapy, the authors have attempted to update the prognostic picture with a review of their results in hydrocephalus that is overt at birth. the status of 37 children treated with cerebrospinal fluid shunts after delivery at term with overt hydrocephalus was evaluated after an average 6-year follow-up period. They represented 8% of all children being followed for hydrocephalus. Outcome was also reviewed in 11 patients with severe hydrocephalus who were not treated. Of treated patients, 86% survived 1 to 16 years, while all of the untreated infants died at an average of 2.5 months. Approximately two-thirds of treated patients have normal or borderline intellectual capabilities (mean IQ 96, standard deviation 22). Dandy-Walker malformation was associated with a high mortality and a very low IQ in survivors. Congenital aqueductal atresia was also associated with intellectual impairment, but children with communicating hydrocephalus and myelomeningocele were not intellectually impaired. Among the survivors with low IQ, the poor outcome was generally predictable on the basis of cortical mantle thickness and "brain mass" calculations before therapy. The findings from this partially selected series indicate that the majority of babies born with overt hydrocephalus have a good prognosis with appropriate therapy.