Gingival scrapings from dogs were examined to determine their aerobic bacterial flora. Of particular interest was the frequent recovery of three unclassified groups of aerobic gram-negative bacteria, IIj, EF-4, and M-5, previously associated with human dog-bite infections. Although no set pattern was found between the variability and consistency of gingival microbiota as related to age, sex, or breed of dog, a certain characteristic flora can be predicted in the healthy canine gingiva. Members of the following genera were found: Streptococcus, Staphylococcus, Actinomyces, Escherichia, Corynebacterium, Pasteurella, Caryophanon, Mycoplasma, Acinetobacter, Moraxella, Neisseria, Enterobacter, and Bacillus.