Injection of dopamine, DOPA or apomorphine into the third brain ventricle resulted in an increase in the plasma testosterone level. Pimozide, blocking dopamine receptors, as well as complete, long-posterior and posterior but not anterior deafferentation of the MBH abolished the stimulating action of dopamine. After direct injection of dopamine into the arcuate nucleus there was no stimulating effect on the pituitary-gonadal system. At the same time, local injections of dopamine and apomorphine into the medial part of the subthalamus or periventricular gray matter of the caudal thalamus were followed by a distinct increase in the plasms testosterone level. The conclusion is drawn that the brain dopaminergic neurons activating the pituitary-gonadal system in the male are localized outside the hypophyseotrophic area of hypothalamus in zona incerta and caudal part of the thalamus. After stimulation of diencephalic dopamine receptors, nervous impulses are transmitted to the MBH through the posterior hypothalamic pathways.