Immunocytochemical method was used to determine the distribution of neurons expressing heme oxygenase-2 (HO-2-positive neurons) in the nuclei of various parts of the brainstem of 16 male Wistar rats. The sizes of neurons and the optical density of the product of histochemical reaction in their cytoplasm were determined in the nuclei studied. HO-2-positive neurons, differing in shape, size and numbers, were identified in the nuclei of the medulla oblongata, pons and midbrain. HO-2-positive cells were found 3-5 times more frequently in the sensory nuclei as compared to the motor ones. At the same time, relatively large number of nuclei was detected, which contained either no or a few HO-2-positive neurons.