Serum specimens were obtained from over 6800 men of Japanese ancestry in Hawaii from 1971 to 1975. Since then, the following numbers of newly diagnosed cancer cases have been identified: 81 colon, 74 lung, 70 stomach, 32 rectum, and 27 urinary bladder. The stored sera of the cases and 302 controls were tested to determine their beta-carotene, vitamin A, and vitamin E levels. There was no association of either vitamin A or E with any of the cancers. For serum beta-carotene, there was a significant association only with lung cancer (20.0 micrograms/dl in cases versus 29.0 in controls, P less than 0.005). The lung cancer odds ratio for men in the lowest quintile of beta-carotene was 3.4 relative to men in the highest quintile. These findings suggest that a low serum beta-carotene level is a predictor of increased lung cancer risk in men.