The degradation of the extracellular matrix is part of many pathological and physiological processes. Of the several proteases involved in extracellular matrix turnover, the plasmin/plasminogen activator system and the family of matrix metalloproteases have received the most attention. Recent investigations in the field of matrix metalloprotease biochemistry have focused on the functions of the various enzyme domains and their interactions with inhibitor domains. Research into physiological activation mechanisms has demonstrated a plasmin/plasminogen activator-metalloprotease cascade, as well as providing an initial characterization of cell surface associated metalloprotease activation.