Standardized tests are increasingly used to determine students' growth in reading comprehension. In some U.S. school districts, the No Child Left Behind Act of 2001 has led to a focus on multiple-choice questions to better prepare students for these types of tests. Even though such questions can provide some important information, they do not enable the teacher to get at the heart of comprehension. To truly understand students' constructed meanings, teachers should use ongoing, classroom-based assignments to distinguish variations in comprehension and adjust instruction. This article describes an authentic classroom-based comprehension assessment process. The authors have been collaborating with one district in Wisconsin where reading specialists and teachers have developed a unified approach to classroom-based assessment of comprehension, and they describe how this process influenced practice. Student examples are provided that demonstrate how one teacher used this assessment process in her fourth-grade classroom to inform instruction and support her students' individual needs. (Contains 1 table and 6 figures.)