AbstractMatrix metalloproteinases are a class of enzymes that play an important role in the remodeling of the extracellular matrix in development and cancer metastasis. This unit describes a set of methods—cell‐mediated dissolution of type‐1 collagen fibrils, direct and reverse zymography, enzyme capture based on α2‐macroglobulin and TIMP‐1 and ‐2, and demonstration of cryptic thiol groups in metalloproteinase precursors—that are used to characterize the functions of matrix metalloproteinases and their inhibitors. Curr. Protoc. Cell Biol. 40:10.8.1‐10.8.23. © 2008 by John Wiley & Sons, Inc.