Over the past few years, several trials on the effect of oral calcium supplementation on blood pressure have been undertaken both in normal subjects and in patients with high blood pressure. Of these, 15 randomized, controlled studies were reviewed: 10 included patients with high blood pressure, three studied normal subjects, and two used a low-calcium diet for comparison. The 15 studies reviewed investigated a total of nearly 400 peoples. No significant evidence for a supine blood pressure-lowering effect of oral calcium supplementation was found in the trials as a whole or in those trials carried out in hypertensives only. However, a small effect on standing blood pressure was detected. Our study indicates that the overall effect of oral calcium on blood pressure, if any, is very small and confined to standing blood pressure, it is, therefore, inappropriate to recommend oral calcium supplementation for the treatment of essential hypertension.