Epichloë typhina is a biotrophic fungal pathogen which causes choke disease of pooid grasses. The anamorphic state, Acremonium typhinum, is placed in the section Albo-lanosa along with related, mutualistic, seed-disseminated endophytes. As an initial study of gene structure and evolution in Epichloë and related endophytes, the beta-tubulin gene, tub2, of the perennial ryegrass choke pathogen (EtPRG) was cloned and sequenced. The coding sequence and the predicted beta-tubulin amino acid sequence were highly homologous to the Neurospora crassa homologs, and to one of the two beta-tubulin genes of Emericella nidulans. However, two introns characteristic of the N. crassa and Em. nidulans genes were absent in the E. typhina gene. Furthermore, one of the remaining introns possessed the uncommon 5' splice junction, GC. In contrast to published observations concerning other Ascomycetes, a mutant of EtPRG, selected for resistance to methyl-2-benzimidazole carbamate (benomyl), possessed no alteration of its beta-tubulin coding sequence.