Asthma was associated with atherosclerotic disease in several studies, with evidence that this association may be limited to women. However, most previous studies failed to account for the heterogeneity of asthma subtypes. We previously reported increased carotid intima-medial thickness in women with adult-onset asthma. In this study, the association of adult- and child-onset asthma with incident coronary heart disease (CHD) and stroke were examined. Subjects were classified according to self-report of physician-diagnosed asthma and age of asthma onset. Cox proportional hazards models were used to test the association of adult- and child-onset asthma with incident CHD and stroke, testing for gender interaction. Subanalysis was also performed using only never smokers. Women with adult-onset asthma experienced a 2-fold increase in incident CHD and stroke that was independent of other risk factors, including smoking, body mass index, and physical activity, and persisted when analysis was restricted to never smokers. No significant association was found in women with child-onset asthma or in men. In conclusion, adult-onset asthma may be a significant risk factor for CHD and stroke in women, but not men.