The importance of low density lipoprotein (LDL) oxidation to the atherosclerotic process has led to the examination of beta-carotene as a possible preventive agent. Several epidemiologic studies show an inverse association between serum/adipose beta-carotene levels and coronary heart disease risk. Randomized clinical trials, however, have not shown any benefit, and perhaps even an adverse effect, of beta-carotene supplementation. A number of possible confounding factors may explain the inconsistency between the trials and epidemiologic evidence. Other carotenoids that are correlated with beta-carotene both in the diet and in the blood might be important factors, as might other plant-derived compounds. Alternatively, low serum carotenoid levels may reflect either increased lipoprotein density or the presence of inflammation, both factors emerging as important novel risk factors for coronary heart disease. Whereas the trial results support no preventive role for beta-carotene, the epidemiologic evidence does generally support the idea that a diet rich in high carotenoid foods is associated with a reduced risk of heart disease.