Nuclear medicine was used to assess the activity of alveolar bone loss in beagle dogs treated with the nonsteroidal anti-inflammatory drug flurbiprofen. Radiographic measurements of the rate of bone loss were taken during a 6-month "pretreatment" period and a 9month treatment period. During the treatment period six dogs received a placebo, and six dogs received orally 0.02 mg/kg flurbiprofen daily for 9 months. In addition, each dog received periodontal surgery in one half of the mouth at the end of the pretreatment period. The rate of alveolar bone loss was significantly decreased in the treatment period in the flurbiprofen-treated dogs (P < 0.001). Measurements of boneseeking radiopharmaceutical uptake were taken 3 months after the initiation of therapy. The single measurement of uptake was compared to the rate of bone loss determined from repeated radiographs taken during the 9-month treatment period. Bone-seeking radiopharmaceutical uptake was an accurate indicator of "active" bone loss in 83.5% of the teeth studied.