Teachers are responsible for using evidence-based practices to improve students' academic and behavioral outcomes. Although teachers have access to a variety of resources on evidence-based practices, poor implementation can adversely affect their effectiveness. However, an inadequate student response to intervention may also be the result of a mismatch between the practice and the student's needs. As a result, it is important for teachers to determine the degree to which they implement evidence-based practices as intended to determine if an inadequate student response is due to poor implementation or inappropriate selection of intervention. The authors discuss the importance of fidelity of implementation. Methods teachers can use to measure implementation fidelity are reported. Suggested methods are discussed and examples are provided.