The ECM remodeling is a finely orchestrated process that involves changes in expression of the ECM genes and the activity of proteinases to clear the previous ECM deposit. Among enzymes involved in ECM remodeling, zinc-dependent proteinases--matrix metalloproteinases (MMPs) are believed to be the ones of major importance. MMPs degrade the ECM components and regulate the bioavailability and/or activity of growth factors by cleavage of both matrix and non-matrix substrates or by mediating receptor turnover. This review introduces the members of the MMP family and discusses their domain structure and function, proenzyme activation and the mechanism of inhibition.