The effect of fluoride on lung tissue was assessed in rabbits during experimental fluorosis. Sodium fluoride as 5, 10, 20 and 50 mg/kg body weight/day was injected subcutaneously for 100 days into rabbits of both sexes. The control animals were given 1 cc distilled water/kg body weight/day for the same period. Histological studies showed alveolar hemorrhage, necrosis of alveolar epithelium and bronchiolitis, followed by progressive exudation of oedema fluid, congestion, and hyperplasia of alveolar cell nuclei in treated animals. In animals of the 50 mg fluoride group, lung parenchyma had a distorted appearance with loss of alveolar architecture. The structural manifestations in pulmonary tissue were more progressive with the subsequent increase in the dosage of fluoride.