Introduction. Most researches on histology of the central nervous system of dolphins are mainly devoted to the morphology of the cerebral hemispheres, while the histology and cytoarchitectonics of the brain stem remain unexplored.Purpose. The anatomical and histological studies of the medulla oblongata of the species Phocoena phocoena relicta.Methods. The anatomical study was carried out by the method of morphometry of the structures of the dorsal and ventral surfaces of the medulla oblongata, histological research - by the Nissl method. Cytoarchitectonics of nuclei and formations was determined from frontal histotopographic sections in the projection on the most expressed macroscopic structures of the organ surface. Digital morphometry data were obtained using the ImageJ program.Results. A macroscopic study showed that olives and triangle of the vagus nerve are the most expressed structures of the medulla oblongata of Phocoena phocoena relicta, while the elevations in the region of the nuclei of the dorsal cord and the triangle of the hypoglossal nerve are not very well delimited or not defined at all.The histological data confirm the results of anatomical morphometry. The dorsal nucleus of the vagus nerve and the lower olive are large and have complex architectonics, while the structure of the nucleus of the hypoglossal nerve and the nuclei of the dorsal cords is more uniform. Along with the lower olive tree, the sensitive nuclei of the trigeminal nerve are of considerable development. The nucleus of the hypoglossal nerve is formed in the ventral horn as a medial motor nucleus.Conclusion. Analysis of the study data shows that the associative - somatomotor (lower olives) and somatosensory cranial-afferent (descending nucleus of the trigeminal nerve) structure achieve significant development in dolphins of the Phocoena phocoena relicta species. The deep delimitation of the dorsal nucleus of the vagus nerve and the formation of the nucleus of the hypoglossal nerve in the somatomotor zone of the ventral horn indicates phylogenetically more ancient features of the morphology of this part of the brain of dolphins.