Bone resorption is one of the hallmarks of inflammatory periapical lesions and is mediated by cytokines. Recent insights into the immunobiology of these lesions indicate that pharmacological modulation of their bone resorbing activity may be possible. Periapical lesions were induced in rats by occlusal exposure of the pulps of their lower first molars. The size of the resulting lesions was followed-up and evaluated by image analysis of their radiographs. The lesions increased with time, and the average area of their radiographic images reached 2.18 (+/- 0.33) mm2 by day 21. Systemic dexamethasone treatment (0.5 mg/kg, every third day) inhibited the growth of the periapical lesions, which reached an average area of 1.63 (+/- 0.30) (p < 0.01). These results support the hypothesis that bone resorption in periapical inflammatory lesions may be pharmacologically down regulated.