Abstract: Two Ophiostomatoid fungi consistently isolated from declining cork oaks attacked bythe ambrosia beetle Platypus cylindrus in Portugal are described as Raffaelea canadensis andR. montetyi. A molecular analysis based on DNA sequences classified these species within theOphiostomatales. The investigation of conidiogenesis of R. canadensis and R. montetyi by SEMsupported this taxonomic placement and showed the formation of conidia by sympodial andannellidic percurrent proliferation, respectively. Also, their pathogenicity was proven throughinoculations experiments. The fungi have been isolated both from wood and the body surface andmycangia of the beetle. It is certain that the pathogens were transferred to cork oak byP. cylindrus, consequently, the previous hypothesis of a species-specific association of a singleambrosia fungus with a single beetle species is questioned.