The recent progress in matrix metalloproteinases (MMPs) research has opened up many cellular targets in a variety of diseases. We have discussed some of the interesting and newly described roles of MMPs in modulating metastatic phenotype in malignancies. This information suggests a more specific and exclusive role of MMPs as important regulators of tumor cell invasion and metastasis. A great deal of room exists for redefining our current understanding of the MMPs system; the more we understand about how MMPs act, the better we will understand the pathobiology of metastasis. Research in the regulation of MMPs and the potential use of MMPs for therapeutic interventions in metastasis continues to expand. The future of therapy involving inhibitors of MMPs as a part of the armamentarium against human neoplasm should be viewed with cautious optimism. This therapeutic approach is beginning to find a place in our understanding of metastatic tumors, but with perhaps few exceptions should still be considered experimental. This area of research now needs more biological knowledge and imagination on the part of investigators to make future achievements possible.