Estimates for a general number of fungal species world-wide are based on the number of vascular plants species, thought to be 270000. It has been argued that the ratio between numbers for vascular plants and for fungi in a given region is 1:6, resulting in a probable general number for fungi of 1620000 (Hawksworth, 1991) or at least not fewer than 1.5 million, of which less than 5% have so far been described (Minter & Dudka, 1996). There are two main sources of information for fungal species diversity in Ukraine, the Handbook of the Fungi of Ukraine (1967-1979) and Fungi of Ukraine. A Preliminary Checklist (1996). The five volumes (seven parts) of the handbook include about 7000 fungal species, known from Ukraine through herbaria and the literature. The checklist includes 5227 fungal names belonging in about 1100 genera of 261 families, 76 orders, 8 classes, 8 divisions and 3 kingdoms. This checklist is almost entirely based on data from the fungal herbarium of the M.G. Kholodny Institute of Botany (KW). Only a small amount of the great bulk of literature devoted to fungi of Ukraine was scanned for the checklist. Analysis of this information shows that only some taxa at an ordinal or familial level have been adequately covered (particularly the Agaricaceae, Amanitales, Diaporthales, Erysiphales, Peronosporales, Sphaeriales, Sphaeropsidales, Uredinales). Numerous other fungal groups have, until now, been almost totally neglected. These include almost all lower fungi, particularly the chytridiomycetes, many orders of hymenomycetes, and especially loculoascomycetes. The situation with basidiomycetes is very similar to that of ascomycetes. Alongside well-investigated groups like the rusts and some of the higher taxa already mentioned, there are economically important groups, such as the Ustilaginales and Aphyllophorales, which need much more attention because information on their species diversity in Ukraine is seriously deficient.