A systematic search for neuroendocrine (NE) cells in the urogenital organs of the pig was carried out by means of Linder's argyrophil method and immunohistochemical techniques. The occurrence, distribution and immunohistochemical character of NE cells (paraneurons) were studied in the vaginal vestibulum, vagina, uterus, oviduct, ovary, urethra, urinary bladder and ureter. In the vestibular glands paraneurons were found to be the most numerous, while a moderate number of these cells occurred in the uterine horn and in the urethra. A distinctly smaller number of paraneurons was present in the oviduct and only occasional NE cells were observed in the urinary bladder. Immunohistochemistry was performed by using the peroxidase-antiperoxidase procedure. Different subpopulations of paraneurons were distinguishable. Chromogranin A-positive paraneurons were found in the vestibular glands, uterine horns, oviducts, urethra and urinary bladder. Somatostatin positivity was observed in NE cells of the vestibular gland, uterine horn, oviduct and urethra. The subpopulation of serotonin-positive paraneurons was present in the vestibular gland and urethra. Bombesin, vasoactive intestinal polypeptide, cholecystokinin, substance P, nitric oxide synthase, beta-endorphin, insulin, adrenocorticotropic hormone, oxytocin and thyroid-stimulating hormone antibodies gave negative reactions in the studied NE cells.