This study was to investigate the effect of calcium supplementation on the reduction of blood pressure in normotensive young adults. Fortyseven healthy college students(23 male and 24 female) were divided into Ca and placebo groups, and were orally given with calcium(1g/day, 2.5g as CaCO3) and placebo, respectively, for 20 weeks. Blood pressure was measured by Korotokoff method in seated position every two weeks. Average daily dietary calcium intakes of the subjects were 626-643mg in men and 513-552mg in women. Average initial level of serum calcium of the subjects belonged to normal range. 1. Both systolic and diastolic blood pressure(SBP and DBP) of Ca group showed significant continuously decreasing tendency from 6-8 weeks until final 20 weeks of the supplementation in both men and women. But placebo groups did not. Comparing with the basal value, reduction of SBP and DBP after 20 weeks were 6.53$pm$4.30%(8.9mmHg) and 8.10$pm$3.30%(7.4mmHg) in men, and 6.56$pm$2.41%(8.1mmHg) and 7.33$pm$3.75%(6.2mmHg) in women. The blood pressure lowering effect of calcium supplementation seemed to be greater in the subjects with higher basal SBP. 2. Serum calcium was significantly increased by calcium supplementation in both men and women, and showed significant negative correlation with SBP(r=-.213) and DBP(r=-.301) in women. Serum Ca/Mg ratio of Ca group was also elevated and showed significant negative correlation with SBP(r=-.174) and DBP(r=-.194) in total subjects. 3. Urinary excretion of Na did not show any significant changes by calcium supplementation in both men and women and showed no correlations with blood pressures.