The powdery mildews (Ascomycota, Erysiphales) are one of the best researched group of fungi in Ukraine, with 108 species of 12 genera recorded (Heluta, 1989). These represent approximately one quarter of all known members of the Erysiphales. Approximately the same numbers of this order are known in neighbouring countries (Bulgaria, 95; Poland, 97; Slovakia, 100; Rumania, 106), suggesting that by 1989 the species of powdery mildews in Ukraine had been fully or almost fully discovered, a view confirmed by the fact that, during the eight subsequent years (1989-1996), only one new species, Microsphaera syringae (Schwein.) Magnus, was found in Ukraine. This species is probably an introduction or a species which has expanded from the far east, because it resembles the far east species Microsphaera palczewskii Jacz. and Microsphaera vanbruntiana W.R. Gerard. in its infection pattern. The last two species penetrated Europe at the end of the 1970s. The new species seems to have completely replaced another parasite of the genus Syringa L. - Microsphaera jaczewskii U. Braun - which now is absent in Ukraine. In addition, during the last few years, Microsphaera magnusii Blumer has been added to the list of powdery mildews presented in the Flora of the Fungi of Ukraine. Its presence in Ukraine previously was doubtful, but has been confirmed by a recent record in the Carpathians. Podosphaera major (Juel) Blumer is another addition, now recognized as a separate species rather than merely a variety of Podosphaera myrtillina (C. Schub.) Kunze). There are also several specimens of Erysiphales from Ukraine which remain unidentified to species level: Erysiphe sp. on Coelosia sp. and Carica papaya, Leveillula sp. on Helianthemum sp., Medicago spp. and Onobrychis spp., Microsphaera sp. on Aesculus hippocastanum L., Chamaecytisus ruthenicus (Fisch. ex Wol.) Klask. and Genista tinctoria L., and Sphaerotheca sp. on Carica papaya. At present, therefore, the list of powdery mildews of Ukraine is no less than 111 species which are distributed by genera as follows: Microsphaera L‚v. (23), Erysiphe R. Hedw. ex DC. (22), Golovinomyces (U. Braun) Heluta (20), Sphaerotheca L‚v. (18), Leveillula G. Arnaud (9), Phyllactinia L‚v. (5), Podosphaera Kunze (5), Uncinula L‚v. (4), Sawadaia Miyabe (2), Arthrocladiella Vassilkov (1), Blumeria Golovin ex Speer (1), and Uncinuliella R.V. Zeng & G.Q. Chen (1). It is possible that this list will be slightly extended if full identification of the remaining collections becomes possible, or if there are further taxonomic changes in the order, or if other alien species invade Ukraine.