Aims: To (i) identify the bacterial communities in the gut of oriental fruit fly (Bactrocera dorsalis) adult and (ii) determine whether the different surroundings and diets influence the bacteria composition. Methods and Results: Polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) fingerprinting was used to investigate bacterial diversity in the oriental fruit fly adult gut. The 16S rDNA cloned libraries from the intestinal tract of laboratory-reared (LR), laboratory sterile sugar-reared (LSSR) and field-collected (FC) populations of oriental fruit fly were compared. Phylogenetic analysis of 16S rDNA revealed that Gammaproteobacteria were dominant in the all samples (73 center dot 0-98 center dot 3%). Actinobacteria and Firmicutes were judged to be major components of a given library as they constituted 10% or more of the total clones of such library. The Flavobacteria, Deltaproteobacteria, Bacteroidetes and Alphaproteobacteria were observed in small proportions in various libraries. Further phylogenetic analyses indicated common bacterial phylotypes for all three libraries, e.g. those related to Klebsiella, Citrobacter, Enterobacter, Pectobacterium and Serratia. libshuff analysis showed that the bacterial communities of B. dorsalis from the three populations were significantly different from each other (P < 0 center dot 0085). Conclusions: (i) The intestinal tract of B. dorsalis adult contains a diverse bacterial community, some of which are stable. (ii) Different environmental conditions and food supply could influence the diversity of the harboured bacterial communities and increase community variations. Significance and Impact of the Study: Comparison of the microbial compositions and common bacterial species found in this paper may be very important for the biocontrol of B. dorsalis.