More than 30 years ago the association between growth hormone and certain tumors was established in animal studies. However, the few clinical studies on acromegalic patients usually failed to demonstrate such a link. It was only recently that acromegaly was found to be associated with other endocrine tumors and with a high incidence of colonic polyps. In a retrospective study we looked for gastrointestinal cancer in 48 acromegalic patients. Five were identified, two cancers of the stomach, two of the colon, and one of the rectum. One patient with stomach cancer and one with sigmoid carcinoma also had recurrent colonic polyps. It is postulated that in our patients, by some yet to be identified mechanisms, the incidence of gastrointestinal cancer is significantly increased in acromegaly.