In a retrospective study of 166 patients, all admitted to the University Hospital, Leiden, The Netherlands, between January 1, 1970 and December 31, 1979, we estimated the relative risk of intracerebral hemorrhage from oral anticoagulant therapy. The risk was more than ten times higher for patients over 50 years of age than for similarly aged untreated individuals in the general population. Within this age group the risk was influenced by neither age nor sex. Hypertension, present in 80% of the patients, was the most important predisposing condition; the risk of bleeding rose with increasing intensity of anticoagulation. There was no substantial difference in clinical condition at onset, rate of progression, mortality, or degree of recovery between patients with anticoagulant-associated hemorrhage and those with spontaneous intracranial hemorrhage.