Certain studies on measures related to central neurotransmitter activity have demonstrated that in delusional (psychotic) depression there is a dopaminergic dysregulation which distinguishes it from non-psychotic depression. A neuroendocrinologic method to check the degree of DA receptor responsivity is by measuring the prolactin responses to acute intramuscular administration of haloperidol. We studied this possibility by applying the haloperidol test in seven delusional and ten non-delusional depressed patients. All patients met DSM-IV criteria for a major depressive episode, single or recurrent, with or without psychotic features. After a three-week washout period, 5 mg of haloperidol were injected i.m. and blood samples were taken at 0, 30, 60, 90 and 120 minutes. In both trials, significant time effects were observed (elevated prolactin levels, F = 11.36, P = 0.000). However, the prolactin responses to haloperidol did not differ significantly between the two patient groups (F = 0.12, P = 0.97). These data do not show a difference in D2 receptor responsivity, at least at the hypothalamus-pituitary level, between psychotic and non-psychotic depression.