We measured plasma levels of lipoprotein(a) (Lp(a)) in a sample of 152 Dutch adolescent mono- and dizygotic twin pairs and their parents. The distribution of Lp(a) levels was skewed, with the highest frequencies at low levels and was similar for adult men and women and their children. The relationship of Lp(a) concentrations with other lipoprotein and apolipoprotein risk factors for coronary heart disease and with lathosterol, an indicator of whole-body cholesterol synthesis, was studied dependent on sex and generation. In mothers and children there was a small positive correlation between Lp(a) levels and plasma cholesterol and apolipoprotein (apo) B. In mothers and daughters there also was a correlation between Lp(a)and LDL cholesterol levels. No correlation was found between Lp(a) levels and plasma lathosterol, suggesting that there is no relationship between Lp(a) levels and cholesterol synthesis. Associations among family members, i.e. between monozygotic and dizygotic twins and between parents and offspring were used to study familial transmission of Lp(a) levels. Results showed that almost all of the variance in Lp(a) concentrations was accounted for by genetic heritability. A small, but significant, sex difference in heritability was observed, but heritabilities were the same in parents and offspring. Heritability estimates were 93% for females and 98% for males. No evidence was found for assortative mating or for the influence of a shared family environment. These results indicate that nearly all variance in Lp(a) concentrations that is not accounted for by the apo(a) size polymorphism, is also under genetic control. © 1993.