The structure, classification, function, and regulation of matrix metalloproteinases in normal and abnormal wound healing is discussed. Results from key studies suggest that neutrophil-derived matrix metalloproteinase 8 (MMP-8) is the predominant collagenase present in normal healing wounds, and that overexpression and activation of this collagenase may be involved in the pathogenesis of nonhealing chronic leg ulcers. Excessive collagenolytic activity in these chronic wounds is possible because of the reduced levels of tissue inhibitor metalloproteinase 1 (TIMP-1). However, until recently, there have been no studies evaluating levels of matrix metalloproteinase or tissue inhibitors of metalloproteinase activity in chronic diabetic foot wounds. Improving basic knowledge and pharmaceutical intervention in this area ultimately may help clinicians identify and proactively intervene in an effort to prevent normal wounds from becoming chronic. This may prevent the high prevalence of morbidity associated with this significant health problem.