In order to clarify the mechanism of elevated iron stores in welder's lungs, the cellular contents of bronchoalveolar lavage (BAL) fluid, the serum iron, total iron binding capacity, liver non-hemin iron and histological findings were examined in experiments using Wister rats exposed to inhalation of welding fumes for 4, 8, Total cell counts, the percentage of neutrophils and iron laden alveolar macrophages in the BAL fluid increased after continuous inhalation, but they were decreased 3 months after inhalation. Serum iron, transferrin saturation, and liver non-hemin iron in rats exposed to inhalation for 8 and 12 weeks were significantly elevated (p<0.01). Iron stores of rats 3 months after inhalation were elevated more than levels 1 week after inhalation. Histological findings in the lung showed a slight thickening of alveolar wall with cellular infiltration. Iron was deposited predominantly in alveolar macrophages of the alveolar space and in connective tissue macrophages. Iron deposition was also seen in the red pulp of the spleen after inhalation. These data suggest that iron was highly stored in the whole body of patients with welder's lung, and that alveolar macrophages play an important role in the iron metabolism of the lung.