Galanin is a 29-amino acid neuropeptide which stimulates the secretion of growth hormone (GH) in normal men. Although the diagnosis of acromegaly involves demonstrating hypersecretion of GH and/or abnormalities in GH secretory dynamics, sometimes it is difficult to establish the activity of the disease. The aim of our study was to assess the response to galanin infusion in acromegalic patients (active and cured). We studied 19 subjects: 5 healthy volunteers (group I), 9 patients with active acromegaly (group II), and 5 with acromegaly cured after transsphenoidal surgery (group III). We performed a test of infusion with porcine galanin (8 microg/Kg/h) to study the secretory response of the GH. Galanin produced a marked increase in GH in the controls, group I (F9,36 = 5.34; p < 0.01) and in the cured patients, group III (F9,36 = 7.35; p < 0.01). On the other hand, galanin did not significantly modify the secretion of GH in the patients with active disease, group II. The areas under the curve (AUC) were higher in groups I and III compared to group II (p < 0.01). Nevertheless, there were no statistically significant differences in the AUC of groups I and III. Our results indicate that the differences in the GH response to galanin in patients with active and cured acromegaly could be of value in the study of the disease.