Using curriculum-specific tools for measuring fidelity of implementation is an essential yet often overlooked aspect of examining relationships among textbooks, teaching, and student learning. This "Brief Report" describes the variety of ways that curriculum implementation is measured and argues that there is an urgent need to develop curriculum-sensitive tools for analyzing classroom practice. It also outlines the use of the Concerns-Based Adoption Model (CBAM) theory to develop analytical tools for measuring implementation of two middle-grades reform mathematics curricula: "Connected Mathematics" and "MathThematics". The report also presents next steps in this program of research. (Contains 2 figures.)