Bacteria isolated from the crop and stomach of laboratory-reared and wild oriental fruit flies,Dacus dorsalisHendel (Diptera: Tephritidae), were identified and tested for attractancy to adult flies in a laboratory olfactometer. Bacteria were identified primarily as belonging to the family Enterobacteriaceae and includedEnterobacter cloacae, E. agglomerans, Klebsiella oxytoca, Citrobacter freundii, andKluyverasp. Bacteria isolated from laboratory flies but found in wild flies includedProvidencia rettgeri, P. stuartii, andSerratiaandCedeceaspp. Attractancy of flies to samples of bacteria cultures, both broth-free (washed) and in broth (unwashed), indicated a relatively low response of flies to these substrates compared with a known attractant, PIB-7 (protein hydrolysate). However, when washed bacteria were tested in the presence or absence of PIB-7 as a treatment, there was a significantly higher response of the flies to the washed bacteria when PIB-7 was absent. Washed bacteria also attracted significantly more flies than water or saline controls. When bacteria were tested as broth cultures (unwashed), they were not significantly different from the broth media in which they were grown. In washed and unwashed bacteria experiments, females showed a greater response than males when treatments were combined for analysis, whereas there were no apparent differences in response among flies of different ages to the combined treatments. Differences in response by sex to the individual treatments revealed significantly greater attraction of females toC. freundiias washed bacteria and toE. cloacaeandK. pneumoniaeas unwashed bacteria.