The relationship between cancer and acromegaly has been subject of study for many years. From a case of differentiated thyroid carcinoma in one of our acromegalic patients, we reviewed a series of 100 acromegalics and found two others cases of thyroid cancer, which are described in this work. From that point, we have got data from the literature about this last association and its possible pathogenesis. The prevalence of thyroid disease is increased among acromegalic patients, mainly due to nodular goiter. This association will be discussed, as well as the relation between insulin-like growth factor-I and cancer, in an effort to have a better understanding of its meaning for our cases. We concluded that it would be prudent to do periodic ultrasonographic evaluation of acromegalic patients, follow by fine needle aspiration biopsies of suspect nodules.