While there are many studies of the distribution of coronary heart disease risk factors in children, adolescents, and middle-aged adults, little information is available on this topic in young adults. The Coronary Artery Risk Development in Young Adults Study (CARDIA) examined 4858 men and women who fasted 10 or more hours, were ages 18 to 30, and were representative of black and white residents of four U.S. communities. Compared with white men, black men had higher age-adjusted mean levels of high density lipoprotein cholesterol (HDL-C) (6.7 mg/dl, p less than 0.001) and apolipoprotein A-l (apo A-l) (9.1 mg/dl, p less than 0.001) and lower concentrations of triglycerides (-19.7 mg/dl, p less than 0.001) and apolipoprotein B (apo B) (-3.3 mg/dl, p less than 0.001). Compared with white women, black women displayed higher concentrations of low density lipoprotein cholesterol (LDL-C) (5.7 mg/dl, p less than 0.001), apo A-l (2.6 mg/dl, p = 0.001), and apo B (3.0 mg/dl, p less than 0.001), but lower triglycerides (-5.8 mg/dl, p=0.001). Gender differences were more pronounced among whites: white men displayed lower mean levels of HDL-C and apo A-l (-9.2 and -7.3 mg/dl, p less than 0.001) and higher concentrations of LDL-C, triglycerides, and apo B (5.2 20.3, and 5.3 mg/dl, p less than 0.001) than white women. Attained level of education was significantly associated with a favorable lipoprotein/apolipoprotein profile, particularly among white women. These data indicate substantial variation in the distribution of lipoproteins and apolipoproteins in young adults, which may be important determinants of future coronary disease risk.