OBJECTIVE To investigate the association of dietary calcium with blood pressure in young children. DESIGN Cohort. SETTING General community. SUBJECTS Eighty-nine boys and girls, aged 3 to 6 years, from The Framingham Children's Study. MEASUREMENTS During the first year of the study, we derived nutrient data from multiple food diaries (a mean of 9.6 days of recording for each subject). At the beginning of the second year of the study, we obtained anthropometric data and up to five blood pressure readings (mean, 4.5) on each child at a single sitting. RESULTS The range of subjects' average daily calcium intake was 4.9 to 19.6 mmol per 4200 kJ, with a mean of 12.8 mmol per 4200 kJ. Subjects' average systolic blood pressure ranged from 73 to 129 mm Hg, with a mean of 95.9 mm Hg; for diastolic blood pressure, the range was 37 to 78 mm Hg, mean 54.6 mm Hg. Multiple linear regression analysis, adjusted for the effects of sex, height, body mass index, and heart rate, showed that for each increment of 2.5 mmol of dietary calcium per 4200 kJ per day, systolic blood pressure was 2.27 mm Hg lower (95% confidence interval, 0.63 to 3.91 mm Hg; P = .008). We found no such association for diastolic blood pressure. CONCLUSION Dietary calcium is inversely related to systolic blood pressure in young children.