AbstractThe predominant cultivable dental plaque flora was studied in 10 adult female beagle dogs with advanced periodontitis. Supragingival and subgingival plaque from a maxillary third premolar (P3) was removed and cultured anaerobically on various growth media and all colonies were subcultured and partially characterized. Histopathological specimens of the plaque sampling sites showed significant loss of connective tissue attachment. Spirochetes were found in ail samples. Anaerobic gram‐negative organisms were predominant in both types of plaque accounting for about 55 % of the cultivable organisms in the supragingival plaque and almost 75% in the subgingival plaque.Bacteroides asaccharolyticuswas the most prominant organism in the supragingival plaque, whereasFusobacterium nucleatumpredominated in the subgingival flora. Streptococcal and actinomycotic species were common in the supragingival plaque, but their proportions, especially those of the actmomycetes, were decreased in the subgingival flora. In many respects the bacterial profile associated with disease resembled that reported in human periodontal diseas