This volume presents current methods to detect and measure the activity of proteolytic enzymes in organisms ranging from unicellular algae to flowering plants. Chapters detail in vitro production, characterization of plant proteases, tools for in vivo modifications, proteomic approaches for identification of substrates, inhibitors and interacting partners, and the function of plant proteases in plant programmed cell death. Written in the format of the highly successful Methods in Molecular Biology series, each chapter includes an introduction to the topic, lists necessary materials and reagents, includes tips on troubleshooting and known pitfalls, and step-by-step, readily reproducible protocols.