Exposure to inorganic dust containing silica particles leads to severe lung dysfunction. In order to evaluate the development of the early changes in pneumoconiosis the studies in rats were performed. Rats were instilled with silica and especially prepared coal dust by tracheal insuflation. After 1, 2, 3, 5, 8, and 10 weeks bronchial lavage was performed and the cells obtained were examined. The lung tissue samples were taken for histological evaluation. To assess the macrophages activity the nitro blue tetrazolium test (NBT-test) was performed. In the groups studied the differences in cell count and populations were found, especially in the monocytes and macrophages group of cells.