The National Assessment of Educational Progress (NAEP) mathematics assessment measures students' knowledge and skills in mathematics and students' ability to apply their knowledge in problem-solving situations. At each grade, students responded to questions designed to measure what they know and can do across five mathematics content areas: number properties and operations; measurement; geometry; data analysis, statistics, and probability; and algebra. The NAEP reading assessment measures students' reading comprehension by asking them to read selected grade-appropriate materials and answer questions based on what they have read. At each grade, students responded to questions designed to measure their reading comprehension across two types of texts: literary and informational. This report presents the results of the 2013 NAEP assessments for reading and mathematics in grades 4 and 8. (Contains 7 figures.) [For related appendices, see ED544346, ED544348, and ED544349.]