Clinical vignette-based surveys have been used for more than 30 years to measure variation in physicians' approaches to the diagnosis and treatment of patients with similar health problems. Vignettes offer advantages over medical record reviews, analysis of claims data, and standardized patients. A vignette-based survey can be completed more quickly than a record review or standardized patient program. Research has shown that vignette-based surveys produce better measures of quality of care than medical record reviews when used to measure differential diagnosis, selection of tests, and treatment decisions. Although standardized patients are preferred when measuring communication and physical examination skills, vignettes are more cost-effective than standardized patients when assessing clinical physicians' decision making. Vignettes offer better opportunities to isolate physicians' decision making and to control case-mix variation than do analyses of claims data sets. Clinical vignette-based surveys are simple and economical tools that can be used to characterize physicians' practice variation.