PCR amplification of 16S rDNA was used to determine the diversity of bacteria associated with 3 strains of sheep scab mite, Psoroptes ovis. Eight species of bacteria were identified by phylogenetic analysis of the PCR product sequences. Seven of these species are previously unreported in association with sheep scab mites. Five species were matched to Serratia marcesens, Proponibacteium acnes, Phyllobacterium rubiacearum, Pantoea agglomerans, Curacaobacter baltica, whereas the remaining 3 sequences matched unclassified sequences belonging to the gamma proteobacteria, pseudomonads and streptococci. Bacterial diversity of the in vivo cultured strain was very low and did not match the diversity of the 2 wild collected isolates. The diversity of the bacteria in relation to the disease of sheep scab and the possible importance of these bacteria in the diet of the mites are discussed.