An unknown species of Ophiostoma was isolated from European larch (Larix decidua) infested by Tetropium gabrieli (Coleoptera: Cerambycidae) and Norway spruce (Picea abies) infested by Tetropium sp. in Austria. The fungus is similar to O. minus, but distinguished from it by the ecology, colony morphologies on OA and MEA, and phylogenetic analysis of aligned DNA sequences of the ITS region of the rDNA operon and the partial beta-tubulin gene. It is described here as O. kryptum sp. nov. The new species readily produces perithecia with short necks and reniform ascospores, and has Hyalorhinocladiella and Leptographium-like anamorphs. Circumstantial evidence suggests that Tetropium spp. act as vectors of O. kryptum. O. minus and O. kryptum represent additional examples of morphologically similar, yet genetically and ecologically distinct species in the genus Ophiostoma. The new combination, O. crenulatum comb. nov. (syn. CeratocYstiopsis crenulata), is also made.