Presumed evolution of low density lipoprotein cholesterol (LDL-C) was studied in a baseline cross-sectional survey of 4955 18-30 year old men and women of various sociodemographic backgrounds. Specifically studied were the influences on LDL-C and the change of LDL-C with age of race, gender, education, diet, physical activity, fatness and fitness. Men increased about 20 mg/dl per 10 years of age, while women increased about 3 mg/dl. Increasing education was found to be associated with higher LDL-C in blacks, but with lower LDL-C in whites. Higher Keys diet score and body mass index were positively associated with LDL-C, while higher total caloric intake, vigorous physical activity, duration on a treadmill exercise test and usual intake of alcohol were negatively associated with LDL-C. The finding of a different relationship of LDL-C to increasing education in whites than in blacks suggests a cultural or behavioral influence in rate of increase in LDL-C.