The 2003 NAAL is a complex assessment with several components and various types of data. The primary purpose of this publication is to describe the assessment's key features and data types. Thus, the publication covers the critical concepts and features carried over from the 1992 assessment, as well as those new to the 2003 assessment--for example, new performance levels that are used to report results (see section 2) and new components that provide expanded data on the least-literate adults and on the role of basic skills in adult literacy performance (see section 3). By providing an overall picture of important goals and aspects of the 2003 NAAL, the publication provides a context for interpreting the results.