Regulated turnover of extracellular matrix (ECM) is an important component of tissue homeostasis. In recent years, the enzymes that participate in, and control ECM turnover have been the focus of research that touches on development, tissue remodeling, inflammation and disease. This volume in the Biology of Extracellular Matrix series provides a review of the known classes of proteases that degrade ECM both outside and inside the cell. The specific EMC proteases that are discussed include cathepsins, bacterial collagenases, matrix metalloproteinases, meprins, serine proteases, and elastases. The volume also discusses the domains responsible for specific biochemical characteristics of the proteases and the physical interactions that occur when the protease interacts with substrate. The topics covered in this volume provide an important context for understanding the role that matrix-degrading proteases play in normal tissue remodeling and in diseases such as cancer and lung disease.