The critically acclaimed laboratory standard for more than forty years, Methods in Enzymology is one of the most highly respected publications in the field of biochemistry. Since 1955, each volume has been eagerly awaited, frequently consulted, and praised by researchers and reviewers alike. Now with over 400 volumes (all of them still in print), the series contains much material still relevant today—truly an essential publication for researchers in all fields of life sciences. Methods in Enzymology is now available online at ScienceDirect — full-text online of volumes 1 onwards. For more information about the Elsevier Book Series on ScienceDirect Program, please visit: http://www.info.sciencedirect.com/bookseries/ This volume is the first of two planned volumes on the topic of small GTPases and their role in disease.