['Patients with brain arteriovenous malformation (AVM) are at life-threatening risk of intracranial hemorrhage (ICH). Identification of genetic variants associated with increased new ICH risk would facilitate risk stratification and guide therapeutic intervention.', 'Brain AVM patients evaluated at University of California, San Francisco or Kaiser Permanente Northern California were followed longitudinally. Primary outcome was new ICH after diagnosis; censoring events were any AVM treatment or last follow-up examination. The association of ApoE epsilon2 and epsilon4 genotype with new ICH was evaluated by Kaplan-Meier survival analysis and further characterized via a Cox proportional hazards model.', 'We genotyped 284 brain AVM patients (50% women; 57% Caucasian; median follow-up time, 0.3 yr) including 18 patients with a history of new ICH). ApoE epsilon2, but not ApoE epsilon4 genotype, was associated with new ICH (P = 0.0052). ApoE epsilon2 carriers had fivefold increased risk of new ICH (hazard ratio, 5.09; 95% confidence interval, 1.46-17.7; P = 0.010; Cox proportional hazards model adjusting for race/ethnicity and clinical presentation). Subset analysis in the largest homogenous ethnic subcohort (Caucasians) confirmed the increased risk of new ICH in ApoE epsilon2 carriers (hazard ratio, 8.71; 95% confidence interval, 1.4-53.9; P = 0.020; multivariate model adjusting for clinical presentation).'] Is apolipoprotein E epsilon 2 associated with new hemorrhage risk in brain arteriovenous malformations?