The natural history of intracranial arteriovenous malformations (AVMs) was studied in 131 patients. The 83 patients managed nonsurgically and the 48 patients treated surgically were followed for an average of 8 years. Hemorrhage occurred in 61.8% of all patients. A second hemorrhage occurred in 67.4% of the survivors of the first hemorrhage. The mortality associated with recurrent hemorrhage did not increase significantly with successive episodes of hemorrhage. The rate of rebleeding was 17.9%/year initially, but declined to 3%/year after 5 years and then to 2%/year after 10 years. Among patients treated nonsurgically, the prognosis was more favorable for patients presenting with seizures than for patients presenting with hemorrhage. Patients in the seizure group had a 26.9% incidence of hemorrhage causing an 11.6% mortality; 40.5% of the patients in the hemorrhage group died. The prognosis was poor for patients with posterior fossa AVMs; the mortality was 66.7% with the first hemorrhage. Recurrent posterior fossa hemorrhage was the rule in survivors, and most of those hemorrhages were fatal. The prognosis for children with AVMs was no different from that for adults.