Ophiostoma europhioides and O. huntii are two very similar fungi known to cause blue-stain of timber. Both species have been isolated from pine and spruce in Canada and are characterized by Leptographium anamorphs and hat-shaped ascospores. The aim of this study was to compare isolates of O. huntii and O. europhioides from various parts of the world. These isolates were compared morphologically using light and scanning electron microscopy. Sexual compatibility was determined using mating studies. O. huntii isolates from the different geographical areas were similar to each other but distinct from O. europhioides. A new Ophiostoma species, O. aenigmaticum, is described for the Japanese isolates; Leptographium aenigmaticum, its anamorph, is described as a new species.