DNA sequence alignment of the nuclear 5·8S ribosomal RNA (rRNA) gene and internal transcribed spacers (ITS) from Beauveria bassiana demonstrated that 6·62% sequence variation existed between nine isolates. A higher level of mutation was observed within the ITS regions, where 8·39% divergence occurred. Polymerase chain reaction restriction fragment length polymorphism, PCR–RFLP, and DNA sequence alignment of the ITS1 and ITS2 regions identified seven polymorphic restriction endonuclease sites, Alu I, Hha I, Hinf I, Sin I, Tru 9AI and two Tha I restriction sites. The allelic frequency of each genetic marker was determined from 96 isolates. PCR–RFLP defined 24 B. bassiana genotypes within the sample set, from which eight phylogenetic clusters were predicted to exist. AMOVA and Fst (θ) indicated that no significant correlation existed between B. bassiana haplotype and insect host range as defined by insect order from which each isolate was derived.