The standardized patient method has often been used to covertly observe and document behaviors in the healthcare setting, through the eyes of a “service user.” A trained person acts as the standardized patient (simulated patient, mystery shopper, pseudopatient, among other terms) and covertly enacts a standardized scenario in the setting of interest. This chapter provides an overview of the standardized patient method, its application in health services evaluation, and practical tips and considerations for designing and conducting evaluations using this method.