The author studied the association of fungi with bark-beetles in material collected in 1933-37 in different parts of Poland. Constant association was observed of Ophiostoma (Ceratostomella) penicillatum, O. polonicum, sp. n., and Graphium pycnocephalum with Ips typographies, L., on spruce, Picea abies (excelsa); of O. (C.) pini and O. (C.) ips with I. sexdentatus, Börn., and O. pini with Myelophilus piniperda[Tomicus piniperda], L., both on pine, Pinus sylvestris; and of O. (Graphium) ulmi with Scolytus scolytus, F., and S. multistriatus, Marsh., on elm, Ulmus foliacea. In addition to these blue-staining fungi, Saccharomycetaceae were constantly associated with all these Scolytids except M. piniperda, and the intensely brown-staining fungus, Stysanus ulmi, sp. n., was an occasional associate of S. scolytus and S. multistriatus. Descriptions of these fungi are given and of many others occasionally associated with the beetles, as well as Latin diagnoses of the new species.