From 1971 to 1975, serum specimens were obtained from 6,860 men of Japanese ancestry in Hawaii. Since then, the following numbers of newly diagnosed cases with epithelial cancer have been identified: 82 colon, 71 lung, 66 stomach, 32 rectum, and 29 urinary bladder. The stored sera of the 280 cases and of 293 randomly selected controls were tested to determine their levels of selenium. There was no association of serum selenium with lung, stomach, or rectal cancer. An increase in relative risk (RR) was noted only for subjects in the lowest quintile of selenium values, as compared to the RR for subjects in the highest quintile, for colon (RR = 1.8) and urinary bladder cancer (RR = 3.1), but neither of these RR estimates was statistically significant (P = .09 and P = .07, respectively). Further work is needed to determine whether the antioxidant properties of selenium protect against specific types of cancer.