Total serum calcium levels were measured in 12 865 men and 14 293 women, between the ages of 25 and 97 years, in the Tromsø Study during 1994 and 1995. With the use of a sex-specific multiple linear regression model with age, calcium, body mass index, cholesterol, HDL cholesterol, triglycerides, systolic and diastolic blood pressure, and pulse as possible covariates, serum calcium was significantly (P<0.001) and positively associated with systolic and diastolic blood pressure, serum cholesterol, and HDL cholesterol in both sexes. A similar but weaker association was observed between serum calcium and triglycerides in men (P<0.01). In all age groups, serum calcium levels were higher in men with a history of myocardial infarction than in those without, and the difference was significant (P<0.0001) in a linear regression analysis adjusted for age. When all the other variables were also included in a logistic regression model, serum calcium was a highly significant (P<0.0001) predictor of myocardial infarction in men, with an odds ratio of 1.2 per 0.1 mmol/L increase in serum calcium. In women, a nonsignificant trend was again seen. Because the free or ionized form of calcium is the physiologically important form and serum calcium was not corrected for serum albumin in our study, the results must be interpreted with caution. However, it appears likely that serum calcium is a predictor of cardiovascular disease in men.