Magnesium plays a role in a number of chronic, disease-related conditions. This article reviews current pertinent literature on magnesium, focusing on hypertension and cardiovascular diseases and implications for relationships with diabetes and metabolic syndrome. A major role for magnesium is in the regulation of blood pressure. While data are not entirely consistent, it does appear that an inverse relationship between magnesium intake and blood pressure is strongest for magnesium obtained from food rather than that obtained via supplements. Hypertension associated with preeclampsia appears to be alleviated when magnesium is administered; in addition, women with adequate intakes of magnesium are less likely to be affected by preeclampsia than those with an inadequate intake. A role for magnesium in other cardiovascular diseases has been noted in that increased magnesium intake may improve serum lipid profiles. Dietary magnesium is also recommended to aid in the prevention of stroke and is important for skeletal growth and development. Magnesium may also play a role in the development of diabetes mellitus, obesity, and metabolic syndrome. There are data from some studies, such as the DASH and PREMIER studies, that suggest that lifestyle changes (including adequate magnesium intake) can benefit blood pressure control, promote weight loss, and improve chronic disease risk.