Though atherosclerosis may have its origins in childhood, intervention studies on coronary heart disease risk factors have usually begun in older adults. Whether young adults exhibit similar relationships of lifestyle to coronary heart disease risk factors, and therefore might be suitable candidates for appropriate intervention, is poorly understood. The Beaver County Lipid Study is a 9-year follow-up study of a free-living young adult population (mean age 22 years) who were initially screened for hypercholesterolemia as seventh grade school children. This report focuses upon cross-sectional correlates of lipid and lipoprotein concentrations in 561 individuals (males n = 262; females n = 299) in 1981-1982. Body mass index was positively related to low density lipoprotein (LDL) cholesterol and triglycerides in men (r = 0.21; p less than 0.001 and r = 0.41; p less than 0.001) and women (r = 0.16; p less than 0.001 and r = 0.20; p less than 0.001). Cigarette smoking was inversely associated with high density lipoprotein (HDL) cholesterol in men (r = -0.11; p less than 0.001) and women (r = -0.20; p less than 0.001) but positively related to triglycerides in both sexes (r = 0.10; p = 0.05 for men and r = 0.19; p less than 0.01 for women). Alcohol consumption was positively related to HDL cholesterol and triglycerides only among men (r = 0.19; p less than 0.001 and r = 0.12; p less than 0.05, respectively). Educational achievement was also positively related to HDL cholesterol in men (p less than 0.01) and women (p less than 0.001). Multivariate analyses indicate that the sex difference in LDL cholesterol was largely eliminated by controlling for body mass index while significant sex differences in both HDL cholesterol and triglycerides remained after controlling for covariates. Results suggest that the known associations in older adults of body mass index and health-related behavior with lipoproteins are well established by young adulthood. Early intervention particularly for obesity may help ameliorate some of the male excess in cardiovascular disease risk.