HDL, VLDL, and LDL cholesterol as well as total cholesterol were measured in young adult offspring of Framingham Heart Study participants. Parental total cholesterol levels measured in the early 1950s were found to be significant predictors of present total cholesterol in the offspring. While both maternal and paternal cholesterol levels made an independent contribution to the prediction of the offspring's cholesterol, the mother's contribution was significantly greater than the father's for male offspring with a similar but less striking relationship for female offspring. The correlation for LDL cholesterol levels for siblings was higher than for HDL cholesterol or log VLDL choles terol. When adjustments were made for age, body weight, alcohol intake and cigarette smoking, slight reductions in the correlations were noted, but all adjusted correlations remained significantly different from zero. The spouse correlations for lipoproteins, however, did not differ from zero after adujustment. Since the significant association for lipoproteins in spouse pairs disappears on adjustment for correlates but the association for siblings does not, it is likely that the sibling lipoprotein associations result from either genetic or environmental factors shared early in life.