Carotid artery intima-media thickness (IMT) is associated with cardiovascular risk factors and is recognized as an important predictive measure of clinical coronary atherosclerosis events in middle-aged and elderly populations. However, information on the association of carotid IMT in young adults with different risk factors measured in childhood, adulthood, or as a cumulative burden of each of the risk factors measured serially from childhood to adulthood is limited. To examine the association between carotid IMT in young adults and traditional cardiovascular risk factors measured since childhood. A cohort study of 486 adults aged 25 to 37 years from a semirural black and white community in Bogalusa, La (71% white, 39% men), who had at least 3 measurements of traditional risk factors since childhood, conducted between September 1973 and December 1996. Association of carotid IMT with risk factors, including systolic blood pressure, lipoprotein levels, and body mass index. Male vs female (0.757 mm vs 0.719 mm) and black vs white (0.760 mm vs 0.723 mm) participants had increased carotid IMT (P<.001 for both). In multivariable analyses, significant predictors for being in top vs lower 3 quartiles of carotid IMT in young adults were childhood measures of low-density lipoprotein cholesterol (LDL-C) level (odds ratio [OR], 1.42, corresponding to 1-SD change specific for age, race, and sex; 95% confidence interval [CI], 1.14-1.78) and body mass index (BMI; OR, 1.25; 95% CI, 1.01-1.54); adulthood measures of LDL-C level (OR, 1.46; 95% CI, 1.16-1.82), high-density lipoprotein cholesterol (HDL-C) level (OR, 0.67; 95% CI, 0.51-0.88), and systolic blood pressure (OR, 1.36; 95% CI, 1.08-1.72); and long-term cumulative burden of LDL-C (OR, 1.58; 95% CI, 1.24-2.01) and HDL-C (OR, 0.75; 95% CI, 0.58-0.97) levels measured serially from childhood to adulthood. An increasing trend in carotid IMT across quartiles of LDL-C level measured in childhood was observed, with a mean value of 0.761 mm (95% CI, 0.743-0.780 mm) for those at the top quartile vs 0.724 mm (95% CI, 0.715-0.734 mm) for those in the lower 3 quartiles (P<.001). Childhood measures of LDL-C level and BMI predict carotid IMT in young adults. The prevention implications of these findings remains to be explored.