Seven species of the Bactrocera dorsalis complex, B. dorsalis, B. papayae, B. carambolae, B. philippinensis, B. occipitalis, B. caryeae and B. kandiensis, were found in a total of 1,093 specimens collected from 136 fruit samples carried by travelers from Asian countries and intercepted by the plant quarantine at Narita Airport of Japan from 1979 to 1998. Two sympatric species combinations, i.e., B. philippinensis vs. B. occipitalis and B. papayae vs. B. carambolae, were distinguished based on aculeus and aedeagal length. However, no difference in aculeus and aedeagal length was found between the other two sympatric species combinations, i.e., B. dorsalis vs. B. kandiensis and B. dorsalis vs. B. caryeae. A comparison of the detection frequency in each host fruit between the two sympatric species of the above two combinations suggests that B. papayae and B. carambolae have different host preferences while B. philippinensis and B. occipitalis have no differences in host preference.