Forty-four Thai isolates phenotypically assigned to the genus Gluconobacter were examined for 16S-23S rDNA ITS restriction analysis by MboII and SduI (=Bsp1286I) digestions. The Thai isolates tested were divided into seven groups: Group I for fourteen isolates, Group IX for one isolate, Group X for two isolates, Group V-2 for four isolates, Group XI for three isolates, Group IV for one isolate, and Group III for nineteen isolates. There were no isolates of either Group II or Group V-1 that were identified as G. cerinus. The isolates of Group III, Group IV, and Group XI were subjected to an additional 16S-23S rDNA ITS restriction analysis by AvaII, TaqI, BsoBI, and BstNI digestions. The isolates of Group III were divided into three groups and two subgroups: Group III-2 for five isolates, Group III-6 for two isolates, and Group III-4, which was divided into two subgroups, Subgroup III-4a for four isolates and Subgroup III-4b for eight isolates. The fourteen isolates of Group I were identified as G. oxydans, and the two isolates of Group X were temporarily identified as G. oxydans. The five isolates of Group III-2 and the one isolate of Group IV were identified as G. frateurii. The remaining twenty-two isolates of Group V-2, Group III-4, Group III-6, Group IX, and Group XI were not identified but are candidates for several new species.