Studies in the beagle dog have clearly established the usefulness of this breed in periodontal disease research. However, little is known about the progressive nature of the disease with advancing age. It is the purpose of this paper to describe frequency and distribution of radiographically detectable lesions in an aging population of 166 colony dogs. 3 grades of alveolar bone loss were determined on high-quality postmortem radiographs. The number of teeth involved was similar in male and female and was age-dependent. Disease was more frequent in the maxillary arcades, with the 2nd upper premolar most frequently involved. Most extensive bone loss was noted around the 3rd and 4th upper premolars, and 1st and 2nd lower molars. It is felt that by the study of such a large group of older colony dogs, a better understanding can be gained of the expected alveolar bone loss with age as determined radiographically.