Matrix metalloproteinases (MMPs) are a group of zinc proteases that serve the function of breaking down extracellular matrix (ECM). The present study evaluated the role of N-acetylcysteine (NAC) on the increased deposition of ECM in hepatic and glomerular fibrosis caused by carbon tetrachloride ($CCl_4$). The activity of MMPs increased and the levels of tissue inhibitors of metalloproteinases 1 and 2 (TIMP-1 and TIMP-2) decreased in the liver and kidney of $CCl_4$-treated rats. Rats treated with $CCl_4$ and NAC showed increased activities of MMPs and decreased levels of TIMP-1 and TIMP-2 in the liver and kidney. Treatment with NAC resulted in the effective degradation of ECM due to an increase in the activities of MMPs and a decrease in the levels of TIMPs.