In terms of their diversity within the habitat, the largest groups of soil micro-arthropods are Collembola and Oribatida. At present more than 2700 species of Collembola from 20 families (Rusek, 1995) and 2500 species of Oribatida from 100 families are known in Europe. Of them 390 and 800 species respectively are known in Ukraine on the basis of published records. In Ukraine diversity hot-spots for soil collembolans are the Carpathians (266 species), the Volyn'-Podillia regions (214) (Kaprus', 1997), the Forest-Steppe zone of the left bank (181) and right bank (108) of the Dnieper (Tarashchuk, 1995). Areas where information about collembolan diversity is lacking are Crimea (26 species recorded), the region adjacent to the Black sea, and Polissia. In western Ukraine 512 species of Oribatida of 74 families are recorded. By number of species the largest superfamilies are Oppioidea and Ceratozetoidea, with 98 and 65 taxa respectively. In the Ukrainian Carpathians 431 orobatid species have been recorded; in Volyn'-Podillia, 383; in Roztochia-Opillia, 282 (Melamud, 1992). Most of the published records during the last 60 years of intensive investigations of collembolans and 40 years of oribatids deal with collections from ecosystems which can be easily attributed to vegetation zones. Investigations embraced soil and litter strata of different types of forest and forest-steppe communities by means of traditional collection methods. Many species in well-defined above-ground and underground habitats thus remain unrecorded. In future special attention should be paid to study of surface ecological groups of collembolans and oribatids in above-ground strata of ecosystems, and using non-traditional collection methods. Micro-arthropod communities in extra- and intrazonal ecosystems are frequently rich in rare species and need special study. On rather specific fauna, almost totally neglected in Ukraine is that of collembolans and oribatids inhabiting narrow spaces between soil and sand particles, and in cave ecosystems. The study of urban habitats would also be promising, as the very diverse conditions there permit the highest levels of micro-arthropod species diversity. Taking into account the imperfect systematics of some groups, and the high diversity of soils and vegetation in Ukraine, a considerable enlargement of the lists of collembolans and oribatids should be anticipated even for well-investigated regions.