AbstractTo determine whether patients with colon cancer metabolizeβ‐carotene differently from benign colon polyp patients, a normal control group (n = 13) and groups of resected colon polyp patients (n = 29) or resected colon cancer patients (Dukes A and BI, n = 21) were supplemented with placebo orβ‐carotene (30 mglday) taken with their morning meals for three months. Serum samples at zero and three months of the study were anlayzed blindly for retinoic acid andβ‐carotene. The results showed thatβ‐carotene levels in the serum of colon polyp and colon cancer groups were 8‐to 12‐fold higher than in the untreated control or the placebo‐treated groups. The benign polyp subjects (n = 17) receivingβ‐carotene showed a significant rise in serum trans‐retinoic acid at three months compared with Time 0. The trans‐retinoic acid values from the colon cancer group receivingβ‐carotene (n = 11) or placebo (n = 10) were significantly lower than the values from theβ‐carotene‐supplemented colon polyp group. It appears that trans‐retinoic acid levels in response toβ‐carotene supplementation are different between treated cancer and benign patients because of different body demands for retinoic acid.