The relationship between parity and coronary heart disease was examined among the women involved in the American Cancer Society's Cancer Prevention Study-II. The total cohort, consisting of 676,526 women, completed a questionnaire concerning medical history, personal health and other issues in 1982. Vital status was determined in 1989. Of the 585,445 women of the cohort who had ever given birth, 4,787 died of heart disease. Parity was added to the established risk factors for coronary heart disease, including age, hypertension, smoking, education, employment, body mass, exercise, and others. An additional follow up analysis was conducted on 2,480 white, postmenopausal women. Among the 585,445 women studied, most birthed two to four children. When all confounders were included in the calculations, the risk of heart disease did not increase with increasing parity. All parous women had a decreased risk of heart disease, compared to nulliparous women. When age was the only confounder, the risk of heart disease increased by 18% for those women with six or more live births, compared to nulliparous women. No trend between increasing parity and heart disease was observed for postmenopausal women. Based on the above analyses, the authors conclude that parity is not a significant risk factor for heart disease among women. Socioeconomic status should be considered a risk factor in the evaluation of this relationship.