Acute Respiratory Distress Syndrome was reproduced in the non-linear male rats by the original method. The animals were injected lysate 45-55 thousand rat neutrophils in 0.2 mi 0.9% sodium chloride solution by puncture of the trachea (method patented RF). At each stage of syndrome development concentration of neutrophil elastase, myeloperoxidase and matrix metalloproteinase-2 in serum and bronchoalveolar lavage fluid was determined by ELISA. The increase of the concentration of neutrophil elastase and myeloperoxidase in plasma and lavage fluid has been shown to be a marker of exudative stage. Proliferative phase is marked by high levels of matrix metalloproteinase-2 at a constant content of elastase and myeloperoxidase in both liquids. Reduction of matrix metalloproteinase-2 concentration in both biological fluids is accompanied by the development of fibrotic phase distress syndrome.