The risk of coronary heart disease is linked to cholesterol levels. Previous studies have reported that the level of human plasma cholesteryl esters is influenced more by genetic factors than the level of free cholesterol. To assess the genetic nature and population differences, a serum cholesterol with free and esterified cholesterol were measured from 22 pairs of twins who ranged from 12 to 26 in age. Thin layer chromatography was used to separate cholestaryl ester and free cholesterol from the rest of serum lipids. No significant contributions of genetic effects were found for any of cholesterol variables. Heterogeneity in variance for the total cholesterol was found in comparison of monozygotic versus dizygotic twins. This might indicated an association of cholesterol variations with twin types as reported previously.