It has been shown that the main psychoactive component of marihuana, delta9-tetrahydrocannabinol (THC) has mainly inhibitory effects on the regulation of reproduction. Recently, the purification and availability of the endogenous ligand of the cannabinoid receptor, arachidonyl ethanolamide, anandamide, (ANA) and its specific long lasting antagonist, the SR 141716 (SR) provided us the opportunity to compare the effects of THC and ANA on the neuroendocrine regulation of reproduction. ANA decreases serum luteinizing hormone (LH) and prolactin (PRL) levels in rats of both sexes. It has no action on serum follicle stimulating hormone (FSH) level. When ANA was administered to pregnant rats it resulted in an increase of the duration of pregnancy and in the frequency of stillbirths. The postnatal development of hypothalamo-pituitary axis in offspring was temporarily inhibited. In conclusion, we found that exogenous and endogenous cannabinoids have only slightly different effects on the reproductive parameters. These effects may occur via the central cannabinoid receptor. It is possible that the sites of action are at both hypothalamic and pituitary levels. The results further support the view that ANA may be a central neurotransmitter or neuromodulator.