Abstract <p>An analysis of the coenoflora of unique botanical and geographical objects, like chalk uplands within the steppe and desert zones of the Russian Federation and the Republic of Kazakhstan, where specific plant communities develop, consisting mainly of calciphytes, is presented. The study area covered five districts of Orenburg oblast of Russia, as well as five districts of the Aktobe and Atyrau regions of the Republic of Kazakhstan. The total flora of the chalk uplands contains 218 species of vascular plants from 35 families and 121 genera. The floristic diversity of chalk uplands reflects their distribution both on the latitudinal gradient and in successional series of plant communities at different stages of overgrowth of chalk rocks. It was revealed that the highest concentration of rare and endemic plant species is characteristic of the massifs of the Sub-Ural Plateau—34 rare plant species from 18 families. Of these, 22 species are included in the Red Data Books at the state level. It is noted that, on the territory of Kazakhstan, where chalk massifs occupy the largest areas, chalks remain largely without a special protection system.</p>