Book excerpt: The Classroom Mathematics Inventory, (CMI) is an informal assessment for use in evaluating students understanding and ability across the range of the elementary mathematics curriculum. Similar to an informal reading inventory, the CMI is an informal classroom assessment tool meant to spark conversations between teacher and student regarding the student's understanding, skills, and attitudes. Using the scripted protocols and included manipulatives, the CMI aids teachers in determining students' performance across the strands of mathematics including: number; extended work with number; algebra; geometry; measurement; and data analysis, statistics, and probability. Additionally, protocols address students' attitudes and mathematical dispositions, as well as their mathematical processes such as problem solving.