This is a review of the most interesting studies on the possible role of sex and gut hormones in gastrointestinal (GI) carcinomas. Many experimental and some human studies suggest that sex and gut peptides may have a growth effect on normal or neoplastic gut cells. It may be possible in the future to develop strategies for patients with GI cancers that will be based upon hormonal manipulation in a manner similar to current strategies that are at present employed in the treatment of patients with breast cancer.