This experiment was designed to investigate the lipid peroxidation and histological effects of chronic fluorosis on first and second generation rat lung tissues. Sixteen, virgin, female Wistar rats were mated with eight males (2:1) for approximately 12 h to obtain first-generation rats. Pregnant rats were divided into two experimental groups (control and fluoride supplemented). The pregnant rats in the fluoride-supplemented group were exposed to 30 mg/L sodium fluoride (NaF) in commercial drinking water containing 0.07 mg/L NaF throughout the gestation and lactation periods. After the lactation period, young animals (first generation; F1) were exposed to the same amount of NaF in drinking water for four months. At the end of the four-month experimental period, nine randomly-chosen male rats (F1) were sacrificed and lung tissues were removed for histopathological and enzymatic lipid peroxidation examination. The second generation rats were obtained from the remaining rats by the same method. They were also treated similarly. At the end of the four-month experimental period, nine randomly-chosen male rats (F2) were sacrificed, and the lungs were removed for histological and lipid peroxidation examination. The rats in the control groups underwent the same procedure without NaF supplementation. It was found that the plasma fluoride and the lung TBARS levels of fluoride supplemented F1 and F2 rats were higher than controls. There were marked histological changes in the lung tissues of fluoride supplemented F1 and F2 rats, as follows: in F1 rats; loss of alveolar architecture, emphysematous areas, descuamation of alveolar epithelium and alveolar congestion were observed. There were thickened interalveolar septae and congestion of alveolar septal vessels. Intraparenchymal thick-walled vessels were also observed. There were markedly perivascular and intraparenchymal focal mononuclear cell infiltrations. In F2 rats, in addition to these changes, there were lipid cell hyperplasia and increased connective tissue mass in the parenchymal areas. It is concluded that chronic fluorosis causes a marked destruction in lung tissues of F1 and F2 rats by causing lipid peroxidation.