We performed multivariate genetic analyses of cardiovascular risk factors from two sets of data on US and Australian female twins. Similar models for body mass index (BMI), serum low density (LDL) and high density (HDL) lipoproteins, including age as a covariate, were fitted successfully to both groups. These suggested that BMI, or genes responsible for a significant proportion of the variance of BMI, explained correlations between lipid subfractions, as well as those between blood pressure and lipid subfractions, especially HDL.