The authors measured the presence and extent of asymptomatic microbleeds on gradient-recalled-echo MRI in 21 aspirin users who developed intracerebral hemorrhage and 21 aspirin users without history of intracerebral hemorrhage. Microbleeds were more frequent (19 vs 7, p < 0.001) and more extensive (mean number of microbleeds 13.3 vs 0.4, p < 0.001) in the intracerebral hemorrhage group than in the control group. Asymptomatic microbleeds may be a risk factor for aspirin-associated intracerebral hemorrhage.