Sheep from a broken‐mouth periodontitis‐affected farm were classified into three groups according to degree of severity of periodontal destruction. Subgingival plaque samples were collected from 10 animals in each group, as well as from 10 sheep from a periodontitis‐free farm, and were plated anaerobically onto a variety of selective and non‐selective media. Results show that several different suspected periodontopathic microorganisms commonly associated with human periodontitis are also present in the plaque of sheep. Black‐pigmentedBacteroideswere associated with the severely‐affected category but there were no significant differences between less severely‐affected groups and healthy animals. This suggests either that sampling may not have coincided with periods of activity in these sheep or that other bacteria may be involved in the initiation of the disease. Type IIFusobacterium nucleatumwas associated with all disease categories when compared to he