The studies were performed on rat's males 4--5 months of age in which pineal glands had been destroyed by electrocaogulation when they were 20--25 days old. These males, submitted to the action of both pCPA and DOPA had stronger reaction to these compounds than the shame operated animals. The administration of pCPA together with COPA was followed by the occurence of very high sexual activity which was accompanied by the decrease in the levels of 5-HT and 5-HIAA and the increase in DA level. DOPA together with Ro-4-4602 did not stimulate sexual behaviour although repeated administration resulted in the increase in DA level and the simulatneous decrease in 5-HT content. In these males, the observed increase in locomotor activity might be responsible for the reduced interest in females accompanying them. It seems that all the three amines play some role in sexual activity since the administration of compounds blocking respective receptors (pimozide-dopamine r., phentolamine-alpha-noradrenergic r., LSD 5-HT system antagonist) to males pretreated with DOPA and showing high sexual activity inhibited sexual activity.