AAGNC are recently found to be one of the most predominant bacterial groups relating to oral diseases, although they had been ignored because of their culture-difficulty. Objective: The aim of this study was to identify AAGNC isolates from endodontic lesions and periodontal pockets using 16S rRNA genes sequencing and G+C content (mol%) analyses. Methods: Genomic DNAs were extracted from 9 strains of AAGNC with InstaGene (Bio-Rad). The 16S rRNA gene was amplified by PCR with universal primers (27F and 1492R) and Premix Taq, and sequenced using a Thermo Sequenase Fluorescent Labelled Primer Cycle Sequencing Kit and an ALFexpress DNA sequencer. The segmented nucleotide sequences of 16S rDNA were integrated using SEQMAN in LASERGENE computer program, then they were applied to GenBank using BLAST and MEGALIGN programs to show the sequence similarities of 16S rDNA among established bacterial species. The G+C content of DNA was measured by high-performance liquid chromatography. Results: The results showed that these 9 strains were divided to 2 groups according to G+C content. Six isolates had 45-46 mol% G+C content, belonging to group I, and were identified to Dialister invisus according to 16S rDNA sequence similarity. The other strains and the reference strain of D. pneumosintes ATCC 33048 had 35-36 mol% G+C content, belonging to group 2, and resembled to D. pneumosintes. However, because their 16S rDNA similarities were not more than 98%, they could not be identified to any established bacterial species. Conclusion: It can be concluded that these oral AAGNC strains have phylogenetic diversities, and new bacterial genera or species may be proposed for some of these AAGNC strains.