The potential effects of inadequate or excessive calcium supply on cardiovascular disease (CVD) are receiving growing attention. We review experimental, epidemiologic, and clinical evidence regarding the role of calcium intake in the development of CVD in adults. In vitro and in vivo laboratory studies have shown that calcium may affect the risk of developing CVD through multiple mechanisms including blood cholesterol, insulin secretion and sensitivity, vasodilation, inflammatory profile, thrombosis, obesity, and vascular calcification. A number of prospective epidemiologic studies have examined the relationship between dietary calcium intake and CVD incidence or mortality in middle-aged and older adults. The results were inconsistent, and the pooled data do not strongly support a significant effect of greater dietary calcium intake on the risk of coronary artery disease (CAD) or stroke. Only a few prospective studies have examined calcium supplement use in association with risk of CVD. The pooled data show no significant benefits of calcium supplement use in reducing the risk of CAD or stroke. No randomized clinical trial has specifically tested the effect of calcium supplementation on CVD as its primary endpoint. Secondary analyses in existing trials to date suggest a neutral effect of calcium (with or without vitamin D) supplements on CVD events, but do not allow for a definitive conclusion. A large percentage of Americans, particularly older adults, fail to meet the US recommendations for optimal calcium intake and are encouraged to increase daily calcium consumption. More prospective cohort studies and large-scale randomized trials are needed to further evaluate the risks or benefits of calcium supplementation on CVD endpoints as the primary pre-specified outcome.