Phage-display technology has begun to make critical contributions to the study of molecular recognition. DNA sequences are cloned into phage, which then present on their surface the proteins encoded by the DNA. Individual phage are rescued through interaction of the displayed protein with a ligand, and the specific phage is amplified by infection of bacteria. Phage-display technology is powerful but challenging and the aim of this manual is to provide comprehensive instruction in its theoretical and applied so that any scientist with even modest molecular biology experience can effectively employ it. The manual reflects nearly a decade of experience with students of greatly varying technical expertise andexperience who attended a course on the technology at Cold Spring Harbor Laboratory. Phage-display technology is growing in importance and power. This manual is an unrivalled source of expertise in its execution and application.