Fusarium strain Fn-2B, a trichothecene producingFusarium strain, first reported asF. nivale but with a very controversial identification, was reexamined genetically by nucleotide sequencing from a highly variable region of the large subunit (25-28S) rRNA (D2 region, ca. 220 nucleotides), and compared to the same region from species it was presumed to belong, in order to assess its phylogenetic affinity.Fusarium strain Fn-2B proved to be more closely related toF. poae NRRL-13637 showing only one heteromorphic site. In comparison to other fungal strains, Fn-2B showed 3,11, and 34 bases that differ fromF. sporotrichioides NRRL-3299,F. triclnctum NRRL-13636 andMicrodochium nivale NRRL-13934, respectively. This phylogenetic affinity between Fusarium strain Fn-2B and F. poae is well correlates with the production of trichothecene mycotoxins by the species.