Joseph Epstein/American Mathematical Society The Calculus Concept Inventory (CCI) was developed by Epstein and a panel of experts to assess students' understanding of differential calculus concepts. The test is intended to be given as a pre-test at the beginning of a first semester calculus course and, again, as a post-test at the end of the course. This article examines CCI development and validation as a concept inventory to examine teaching methodology and curricula issues that prevail for undergraduate mathematics.