This document describes the Prescription Behavior Surveillance System (PBSS), which uses de-identified prescription drug monitoring program (PDMP) data from multiple states to conduct public health surveillance and evaluate initiatives aimed at influencing prescriber behavior. The PBSS is guided by a committee including federal and state partners and aims to identify emerging trends, changes in prescribing patterns, and indicators of risk. It provides regular surveillance reports and measures of appropriate/inappropriate prescribing. The PBSS also evaluates selected state prescriber initiatives and their evidence base. Examples of surveillance data and potential additional applications are provided.