Acute respiratory distress syndrome (ARDS) was reproduced in rats by endotracheal administration of 45-55 thousand lysed rat neutrophils (RF patent). In each stage of the syndrome, immunohistochemistry was used to determine the expression of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor type 2 (MIMP-2) by lung cells. It was found that there was a substantial increment of MMP-2 expression in the fibroblasts, macrophages, endothelium, and fibroblasts in the exudative stage of ARDS. In its proliferative stage, the expression of MMP-2 remained high in the neutrophils and type II alveolocytes, by reducing in the macrophages, endothelium, and fibroblasts. In the fibrotic stage, it returned to the level of the control group only in the macrophages and type II alveolocytes, by remaining high in the other cells, as before. In progressive ARDS, the expression of TIMP-2 increased only in the neutrophils, endotheliocytes, and fibroblasts, remaining to be equal over all stages.