While recent studies have reported an inverse relation between childhood intelligence test scores and all-cause mortality in later life, the link with disease-specific outcomes has been rarely examined. Furthermore, the potential confounding effect of birthweight and childhood social circumstances is unknown. We investigated the relation of childhood intelligence with coronary heart disease (CHD) and stroke risk in a cohort of 6910 men born in 1953 in the Copenhagen area of Denmark. Events were ascertained from 1978 to 2000 using a cause-of-death register and hospital discharge records. There were 150 CHD (19 fatal; 131 non-fatal) and 93 stroke (4 fatal; 89 non-fatal) events during follow-up into mid-life. Childhood intelligence was inversely related to CHD with the highest rate apparent in adults with low childhood test scores (HR(lowest vs. highest quartile), 2.70; 95% confidence interval: 1.60, 4.57; P(trend) = 0.0001). After adjustment for paternal social class and birthweight, this association was attenuated only marginally. There was little evidence of a IQ-stroke relationship. The cognitive characteristics captured by IQ testing in the present study, such as communication and problem solving ability, appear to be associated with risk of CHD. Health promotion specialists and clinical practitioners may wish to consider these skills in their interactions with the general public. Replication of these results using studies which hold data on intelligence and socio-economic position across the life course is required.