Matrix metalloproteinases (MMP) have been implicated in a variety of diseases in which the destruction of connective tissue is an important pathological event. These include osteo and rheumatoid arthritis, tumor metastasis and angiogenesis, and corneal ulceration. As a result, there has been a great deal of activity directed towards the design of MMP inhibitors as therapeutic agents for the treatment of these conditions. Progress in the field has now evolved to a degree where potent, low molecular weight, orally active inhibitors have been discovered and advanced to clinical trials. While a majority of inhibitors are dipeptide derivatives, a non-peptide, orally active inhibitor has recently been reported. Some success has also been achieved in the design of subtype selective MMP inhibitors. The elucidation of X-ray and 0NMR structures of several MMPs, and the ability to create homology models of others has provided an understanding of some of the structural requirements leading to potency and specificity. Herein is a review of recent advances in the biology and chemistry of MMPs and MMP inhibitors, including the association of MMPs with specific disease processes, structure activity relationships of MMP inhibitors and factors affecting enzyme specificity and their correlation with MMP structure.