Adult male Sprague-Dawley rats (average weight 530-540 g) were studied in two different series. In series I, studying disuse osteopenia, the experimental rats had all maxillary molars extracted on one side. After 16 wk they had their mandibular first molar of the corresponding side extracted and were followed for another 4 wk. In series II, studying calcium deficiency osteopenia, the experimental rats were given a low calcium diet for 16 wk and at this time had their mandibular first molars extracted. Both disuse and calcium deficiency caused osteopenia, which did not seem to impair the healing process after tooth extraction in the short term. One puzzling finding in the disuse series (I) was that the alveolar height at the extraction site was higher in the experimental than in the control group 4 wk after extraction.