To support their efforts to promote high quality and efficient care, policymakers need to better understand the key factors associated with variations in physicians' decisions, and in particular, physician deviations from evidence-based care. Clinical vignette survey instruments hold potential for research in this area as an approach that both allows for practical, large-scale study and overcomes the data quality challenges posed by analysis of clinical data. These surveys present respondents with a narrative description of a hypothetical patient case and solicit responses to one or more questions regarding the care of the patient. In this review, we describe various methods for measuring variations in physicians' decisions and highlight a range of design features researchers should consider when developing a clinical vignette survey. We conclude by identifying areas for future research.