To verify the diagnostic capacity of some dynamic tests of the prolactin (Prl) secretion, the findings obtained by high-resolution computed tomography (CT) were compared with results obtained from tests using nomifensine (NOM) domperidone (DOM) and thyrotrophin-releasing hormone (TRH) in 72 patients with pathological hyperprolactinaemia. None of the patients with tumours had a positive Prl response to NOM or to DOM administration; however, a positive response to these tests was present in only 24 and 41%, respectively, of the patients with normal CT picture. The results of TRH testing were similar to those obtained with DOM. Different neuroendocrine patterns were disclosed by comparing pituitary Prl and thyrotrophin (TSH) responses to DOM: 1) some subjects had a reduced Prl response together with an exaggerated or normal TSH response to DOM; they comprised patients with tumour, empty sella, and normal CT picture; 2) other patients with normal CT picture had a positive Prl and a normal TSH response to DOM. These results demonstrate that a negative Prl response to NOM and DOM characterizes all patients with adenoma; however, the tumour-like responses in patients with no visible tumours seem to reduce the diagnostic value of these tests, unless the latter may predate the radiological appearance of an adenoma. On the other hand, a positive Prl and a normal TSH response to DOM exclude the presence of a pituitary tumour. This diagnostic finding is strengthened by the positive response also to NOM. Whatever may be the diagnostic validity of dynamic tests, they provide sound information on the functional state of dopamine neurotransmission.