Relative volumes of mitochondria (MIT), lysosomes (LYS), Golgi profiles (GP), granular endoplasmic reticulum (GER), membrane bound bodies of type 1 (MBB 1) and type 2 (MBB 2), and the number of dense-core vesicles (DCV), were counted in pinealocytes of female sexually immature pigs, in animals in oestrus and in nursing pigs. Relative volumes of GER, LYS, MBB I and the number of DCV changed in the different stages of the sexual cycle. The highest volumes of GER, LYS and MBB 1 were observed in pigs in oestrus. Pinealocytes of sexually immature pigs were characterized by a considerably higher number of DCV in comparison with mature animals.