The goal of augmentative and alternative communication (AAC) is the most effective communication possible. Speech-language pathologists are obligated to collect data, measure communication, and apply the principles of evidence-based practice (EBP). This article presents a model for EBP that represents how collecting and evaluating performance data supports clinical decisions. The three components of EBP are discussed: (1) field evidence, (2) evidence at the personal level, and (3) clinician experience. Language activity monitoring or data logging are offered as one approach of collecting performance data. Software tools such as the AAC Performance Report Tool (PERT) for reporting language skills and communication competence are described. A clinical example is incorporated to show the application of EBP and performance measurement.