The matrix metalloproteinases are a tightly regulated family of enzymes that degrade extracellular matrix and basement membrane components. Recent evidence suggests that these proteases and their specific inhibitors play important roles in normal developmental processes and in pathological conditions. MMP-11, a new member of the matrix metalloproteinase family, is expressed in tissues undergoing the active remodeling associated with embryonic development, wound healing and tumor invasion. But like all other members of the matrix metalloproteinase gene family, stromelysin-3 is synthesized as an inactive precursor that must be processed to its mature form in order to express enzymic activity. MMP-11, like an inflammatory mediator, may exert a chemotactic influence on macrophages which aggregate in the mesangium.