Seven mathematics textbook series used for Grades 1 through 8 in the United States were examined. Textbook pages were counted as arithmetic, measurement, geometry, data analysis, or algebra. Percentages of mathematics textbook content were compared with percentages of mathematics content on the Ohio Ninth Grade Proficiency Test. Areas of greatest mismatch were arithmetic, measurement, and algebra. The overall percentage of arithmetic in the textbook series was about twice that on the test; the percentage of measurement was less than half that on the test; and the percentage of algebra was a third or less than that on the test. Results are also presented by grade level, and implications for teaching are discussed.