This document provides an overview of the 1980 and 1981 Illinois Inventory of Educational Progress (IIEP) in mathematics. Development of the IIEP is discussed, and results and analyses of the tests administered to students in grades 4, 8, and 11 are presented. Test items are included. Factor analysis identified two factors, "knowledge of mathematical skills and relationships" and "mathematical problem-solving ability." Appendices include answer keys, tables of mathematical items and objectives, and a list of available documents on the IIEP. (MNS)