This report examines the correlation of serum apoprotein D with other lipoprotein lipids and apoproteins in a healthy, male population and compares the levels of high density lipoprotein apoprotein D of this control population with 2 samples composed of male, acute myocardial infarction patients and their healthy, male, first-degree relatives. Highly significant correlations were observed with very low density lipoprotein lipids (negative), high density lipoprotein lipids (positive) and serum triglycerides (negative). Serum and low density lipoprotein apoprotein B was not correlated with serum apoprotein D, whereas apoprotein A-I from serum and high density lipoproteins was strongly correlated with apoprotein D. A significant reduction in high density lipoprotein apoprotein D was observed in male, myocardial infarction patients. Their male, first-degree relatives also had lower apoprotein D levels, but the difference was not significant.