This study was performed in order to establish the secretory patterns and the possible relationships between the adrenocorticotropin (ACTH)/cortisol and arginine vasopressin (AVP) responses in normal men to the systemic administration of ghrelin, an endogenous ligand for the growth hormone secretagogue receptor. For this purpose, a bolus of 1 µg/kg ghrelin was injected intravenously in 9 normal men. AVP, ACTH and cortisol significantly rose in response to ghrelin injection; however, in all subjects the AVP rise preceded the ACTH/cortisol responses. In fact, the mean peak levels of AVP, ACTH and cortisol after ghrelin injection were observed at 15, 30 and 45 min, respectively. When peak AVP responses to ghrelin were considered together with ACTH and cortisol peak levels, highly significant positive correlations were observed (AVP and ACTH, r = 0.94, p < 0.001; AVP and cortisol, r = 0.92, p < 0.001). In conclusion, this study shows that the AVP response to ghrelin precedes the concomitant ACTH/cortisol rise and that these hormonal responses are highly positively correlated. These observations support the hypothesis that AVP mediates ghrelin-induced ACTH secretion in normal men.