In recent years, it has become increasingly recognized that acromegaly predisposes to a variety of cancers, particularly colorectal and breast cancers, and perhaps haematological malignancies. However, these associations haze been based mostly on small epidemiological surveys, and a propensity towards other malignancies might also become apparent in the future. This review assesses these three malignancies together with those of the thyroid and pi-estate, and discusses their pathogenesis, concentrating on the role of the growth hormone/insulin-like growth factor I (IGF-I) axis.