The distribution of substance P (SP), vasoactive intestinal polypeptide (VIP) and serotonin (5-HT) containing structures in the central nervous system of the lizard, Lacerta agilis, were investigated with the aid of the peroxidase-antiperoxidase immunohistochemical method. SP and 5-HT nerve fibers are found almost all over the brain, whereas VIP fibers are mainly observed in the limbic area, in the periventricular gray matter of the diencephalon and in the brain stem. The cells of origin are located in the telencephalon for the SP, in the mesencephalic tegmentum for the VIP, and in the midline and the basis of the brain stem for the 5-HT. In addition to the known paraventricular organ in the diencephalon VIP and 5-HT immunoreactive cells are found in the ependymal layer of the rostral part of the lateral ventricle.