Used worldwide in assessment and professional certification contexts, computerized adaptive testing (CAT) offers a powerful means to measure individual differences or make classifications. This authoritative work from CAT pioneer David J. Weiss and Alper Şahin provides a complete how-to guide for planning and implementing an effective CAT to create a test unique to each person in real time. The book reviews the history of CAT and the basics of item response theory used in CAT. It walks the reader through developing an item bank, pretesting and linking items, selecting required CAT options, and using simulations to design a CAT. Available software for CAT delivery is described, including links to free and commercial options. Engaging multidisciplinary examples illustrate applications of CAT for measuring ability, achievement, proficiency, personality, attitudes, perceptions, patients’ reports of their symptoms, and academic or clinical progress.