Collagenases are an important subfamily of matrix metalloproteinases utilizing native collagens as a substrate. This book reviews a current knowledge of the structures and functions of collagenases and the roles they play in development, tumor metastasis, and tissue remodeling during wound healing. This review comes at a time when new collagenases are being discovered, such as collagenases, rather than all matrix metalloproteinases so that a more thorough examination of the function of this crucial set of enzymes in a variety of systems can be achieved. Because of the great deal of work that has gone into understanding this group of enzymes, the findings in this area may also serve as useful paradigms for work in related areas.