The purpose of T Cell Protocols: Development and Activation is to c- lect a series of protocols, particularly those that have been developed within the past few years, to help investigators master new techniques (or improve existing ones) for the study of T-cell Biology. Invariably, in putting together a book like this it is difficult to decide which methods to include and which to leave out. To this end methods were selected from a variety of disciplines, including cellular immunology, b- chemistry, and molecular biology, to try to provide something of interest for everyone who works on T-cell development and activation. I would like to mention that my primary reason for agreeing to put this book together is that, when I was a graduate student, I purchased a copy of Selected Methods in Cellular Immunology by Mishell and Shigii which proved a tremendous help in learning the basics of one-and two- dimensional gel te- niques (and other methods). The cover has long since fallen off, but it still remains one of my most valued reference books for the laboratory. It is my hope that T Cell Protocols: Development and Activation will prove similarly useful to current and future scientists wishing to learn new methods for expl- ing the development and activation of T cells.