Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin gene, involves severe muscle degeneration, inflammation, fibrosis, and early death in afflicted boys. Matrix metalloproteinases (MMPs) are extracellular proteases that cause tissue degradation in several disease states. In this study, we tested the hypothesis that the expression levels of various MMPs are abnormally increased and that their inhibition will ameliorate muscle pathogenesis in animal models of DMD. Our results show that the transcript levels of several MMPs are significantly up-regulated, whereas tissue inhibitors of MMPs are down-regulated, in dystrophic muscle of mdx mice. Chronic administration of batimastat (BB-94), a broad spectrum peptide inhibitor of MMPs, reduced necrosis, infiltration of macrophages, centronucleated fibers, and the expression of embryonic myosin heavy chain in skeletal muscle of mdx mice. Batimastat also reduced the expression of several inflammatory molecules and augmented the levels of sarcolemmal protein beta-dystroglycan and neuronal nitric oxide in mdx mice. In addition, muscle force production in isometric contraction was increased in batimastat-treated mdx mice compared with those treated with vehicle alone. Furthermore, inhibition of MMPs using batimastat reduced the activation of mitogen-activated protein kinases and activator protein-1 in myofibers of mdx mice. Our study provides the novel evidence that the expression of MMPs is atypically increased in DMD, that their inhibition ameliorates pathogenesis, and that batimastat could prove to be a significant candidate for DMD therapy.