Acromegaly is characterised by excessive levels of circulating growth hormone and its tissue mediator, insulin-like growth factor (IGF)-I. Prior to effective treatment and lowering of growth hormone and IGF-I, the majority of patients with the disease died by the age of 60 years, largely due to diabetes mellitus, cardiovascular and cerebrovascular diseases. More recently, it has become apparent that patients with acromegaly may also have an increased prevalence of colorectal adenomas and cancer. This may be due to elevated IGF-I, which is implicated in the development of sporadic colorectal cancer, and environmental factors, such as the bile acid deoxycholic acid, the levels of which are also increased in acromegaly. There is some evidence to suggest that breast and prostatic malignancies might also be increased in acromegaly. However, these associations have been based mostly on small epidemiological surveys and circumstantial evidence. Large-scale epidemiological studies are required to clarify this issue.