The studies were carried out on the hypothalamus of bison banasus aged 2 and 3 months. Sections were made by means of Bagiński's technique and Nissl and Klüver-Barrera methods. Four types of neurons were distinguished in the paramamillary nuclei: nucleus supramamillaris (Sm) and nucleus tuberomammillaris pars posterior (Tmp). Type I small and, medium-size, triangular or fusiform cells, which have 2-3 slender, poorly ramified dendrites; typical leptodendritic neurons. Type II, medium size neurons with quadrangular or spindle-shaped perikaryons. Most of them have 3-4 thick dendritic trunks with ramifying relatively long dendrites. These cells show stalked-appearance and possess different appendages sparsely distributed. Type III is similar to type II, but is made of medium-size to large multipolar cells having quadrangular, triangular or fusiform perikaryons and relatively short dendrites. Type IV, small and rnedium-size, globular cells with 2 or 3 dendritic trunks, which dichotomously subdivide into quaternavy dendrites. In all types of neurons, axons emerge from the perikaryon or initial portion of a dendritic trunk. Type I was found in both studied nuclei. Types II and III constitute mainly the nucleus tuberomamillaris pars posterior. Type IV preponderate in the nucleus supramamillaris. The characteristic feature of Tmp cells, in Nissl picture was irregular contour of the somas and clumps of rough Nisls granules, which appear to lie outside the perikaryons. In Sm there were also lightly stained small rounded cells having both small amount of the cytoplasm and tigroid matter.