Prospective, multisite study to examine whether (CPV®) vignettes accurately measure the quality of clinical practice by using a comparison with standardized patients (the gold standard method), and to determine whether vignettes are a more or less accurate method than medical record abstraction. Physicians scored: 68% (CI, 67.9% to 68.9%) when measured by the vignettes but only 63% (CI, 62.7% to 64.0%) when assessed by medical record abstraction. These findings were consistent across all diseases and were independent of case complexity or physician training level. (CPV®) vignettes also accurately measured unnecessary care. Thus, (CPV®) vignettes are a valid tool for measuring the quality of clinical practice. They can be used for diverse clinical settings, diseases, physician types, and situations in which case-mix variation is a concern.