The results of the revision of the species composition and related knowledge of taxonomy, biogeography, diagnostics, variability and ecomorphology of polytypic groups of murine rodents, superfamily Muroidei, are presented. These are 5 former "large" species: "wood mice", "common mice", water voles, "shrub voles" and "common voles". Each of these groups is represented in the fauna of Ukraine and neighboring countries by 2–3 species. The two most difficult for revision and for background monitoring of fauna are "forest mice" and "common voles", each of which is represented in the fauna of the region by three morphologically very similar species of different kinship, among which one (the most genetically distant) is widely sympatric to the other two species that are allospecies. Among "forest mice", such species are Sylvaemus uralensis (= microps) against the pair S. sylvaticus + S. witherbyi (= S. falzfeini), and among the "common voles" it is Microtus levis (= rossiaemeridionalis) against the pair M. arvalis + M. obscurus. The other three pairs of species are generally more diverged (at least in terms of habitats and ecology, and in some cases morphology) and clearly less sympatric species. In the group of "common" mice, Mus "musculus" (s.l.), there is a pair of synanthropic and exanthropic forms — M. musculus and M. spicilegus (= M. sergii), which usually do not interact in nature, and therefore poorly diverged in morphology. In the group of "water voles" there is an allopatric pair, represented by the Carpathian-Roztochchian (essentially mountainous, associated with meadows) as well as plain hydrophilic forms, Arvicola scherman and A. amphibius (= A. terrestris). In the group of "shrub voles" there is a sympatric pair of species, one of them has limited distribution in the Carpathians (Terricola tatricus), but the other (T. subterraneus), being sympatric to the first in the Carpathians, also forms numbered populations in lowland forests, as in the forest zone as in the bairak steppe zone. Morphological differentiation between them is generally high, but the Eastern Carpathian form of Terricola tatricus is the smallest in a row of mountain forms of Terricola (multiplex, tatricus, zykovi), which was the reason for its long-term non-recognition in the fauna of Ukraine. For all species, descriptions are presented, including 5 standard parts for this series of publications: general remarks, taxonomy (including nomenclature), distribution (including biotopes), diagnostics (including variability), ecomorphology.Key words: small mammals, habitats, dominance, abundance of species.
