From the somewhat conflicting published data on apolipoprotein E (apoE) genotype in hemorrhage due to cerebral amyloid angiopathy (CAA), it is unclear whether apoE genotype influences the risk of CAA-related hemorrhage independently of its association with concomitant Alzheimer's disease (AD). We determined the apoE genotypes of 36 patients presenting with cerebral hemorrhage associated with histologically confirmed CAA. The frequency of apoE ϵ2 was 0.25 and the frequency of apoE ϵ4 was 0.18. Patients with CAA-related hemorrhage and concomitant AD pathology (CERAD criteria, n = 17) had a high apoE ϵ4 frequency, close to that in AD cases without hemorrhage. Patients in whom CAA-related hemorrhage occurred in the absence of significant AD pathology (n = 13) had an apoE ϵ4 frequency somewhat lower than non-AD controls without hemorrhage. However, in CAA-related hemorrhage, the apoE ϵ2 frequency was high regardless of whether significant AD pathology was present. We conclude that whereas possession of apoE ϵ2 may be a risk factor for cerebral hemorrhage due to CAA, apoE ϵ4 is a risk factor for concomitant AD but not an independent risk factor for CAA-related hemorrhage.