BACKGROUND: Parity is associated with coronary heart disease (CHD) risk. In the present study, we assessed the associations between number of children and CHD in both women and men. METHODS AND RESULTS: A total of 4286 women and 4252 men aged 60 to 79 years from 24 British towns were studied. Number of children was positively associated with body mass index and waist-hip ratio in both sexes. In women but not in men, number of children was inversely associated with high-density lipoprotein cholesterol and was positively associated with triglycerides and diabetes. For both sexes, similar "J" shaped associations between number of children and CHD were observed, with the prevalence lowest among those with 2 children and increasing linearly with each additional child beyond 2. For those with at least 2 children, each additional child increased the age-adjusted odds of CHD by 30% (odds ratio, 1.30; 95% confidence interval, 1.17 to 1.44) for women and by 12% for men (odds ratio, 1.12; 95% confidence interval, 1.02 to 1.22). Adjustment for obesity and metabolic risk factors attenuated the associations between greater number of children and CHD in both sexes, although in women some association remained. CONCLUSIONS: Lifestyle risk factors associated with child-rearing lead to obesity and result in increased CHD in both sexes; biological responses of pregnancy may have additional adverse effects in women.