Cognitive diagnosis models originated in the field of educational measurement as a psychometric tool to provide finer-grained information more suitable for formative assessment. Typically,but not necessarily, these models classify examinees as masters or nonmasters on a set of binary attributes. This chapter aims to provide a general overview of the original models and the extensions, and methodological developments, that have been made in the last decade. The main topics covered in this chapter include model estimation, Q-matrix specification, model fit evaluation, and procedures for gathering validity and reliability evidences. The chapter ends with a discussion of future trends in the field.