The U.S. PIAAC Survey of Incarcerated Adults was designed to provide policymakers, administrators, educators, and researchers with information to improve educational and training opportunities for incarcerated adults and foster skills they need in order to return to, and work successfully in, society upon release from prison. This report highlights data from the survey's extensive background questionnaire and direct assessments of cognitive skills. It examines the skills of incarcerated adults in relationship to their work experiences and to their education and training in prison. Results for incarcerated adults on the literacy and numeracy domains are presented in two ways: (1) as scale scores (estimated on a 0-500 scale), and (2) as percentages of adults reaching the proficiency levels established for each of these domains. The report includes results for groups of incarcerated adults by various characteristics, including employment prior to incarceration, experiences with prison jobs, skills certifications, educational attainment in prison, and participation in academic programs and training classes. The following are appended: (1) Methodology and Technical Notes; (2) PIAAC Scales and Proficiency-Level Descriptions; and (3) Members of the PIACC Prison Expert Group. [The research contained in this document was coordinated in part by the Texas Department of Criminal Justice.]