The 28.5-kbp mitochondrial (mt) genome from the entomopathogenic fungusBeauveria bassianawas studied using restriction enzyme analysis, gene probe hybridization, and DNA sequence comparisons. A detailed restriction enzyme map allowed cloning of the entire genome into a number of segments. Hybridization of heterologous gene probes to the mtDNA resulted in the identification of the large ribosomal RNA (lrRNA) and small ribosomal RNA (srRNA) genes. Gene probes derived from several yeasts and fungi failed to identify any additional genes. However, partial DNA sequence analysis revealed thelrRNAandsrRNAgenes as well as four protein-encoding genes: the NADH dehydrogenase subunit 1 (NAD1), NADH dehydrogenase subunit 6 (NAD6), cytochrome oxidase subunit 3 (C03), and ATPase subunit 6 (ATP6) genes. The ATPase subunit 9 (ATP9) gene was not identified by hybridization to mtDNA, but could be detected by hybridization to total cellular DNA. The portions of the genes sequenced were homologous to the equivalent genes from yeast and other filamentous fungi, most notablyAspergillus nidulans. No introns were identified in these regions. The organization of the sequenced region of theB.bassianamt genome more closely resembled that ofA.nidulansthan that ofPodospora anserinaorNeurospora crassa.Key words:Beauveria bassiana, mtDNA, gene mapping, mitochondrial rRNA, mitochondrial organization.