The National Assessment of Adult Literacy (NAAL) is a household survey conducted periodically by the Department of Education that evaluates the literacy skills of a sample of adults in the United Stages ages 16 and older. NAAL results are used to characterize adults’ literacy skills and to inform policy and programmatic decisions. The Committee on Performance Levels for Adult Literacy was convened at the Department’s request for assistance in determining a means for booking assessment results that would be useful and understandable for NAAL’s many varied audiences. Through a process detailed in the book, the committee determined that five performance level categories should be used to characterize adults’ literacy skills: nonliterate in English, below basic literacy, basic literacy, intermediate literacy, and advanced literacy. This book documents the process the committee used to determine these performance categories, estimates the percentages of adults whose literacy skills fall into each category, recommends ways to communicate about adults’ literacy skills based on NAAL, and makes suggestions for ways to improve future assessments of adult literacy.