Regardless of the direction US health care reform takes, performance measurement, public reporting, and accountability will play major roles. Presently, a number of entities have staked out business models for developing, collecting, and disseminating operational data about performance at the hospital, health plan, and clinician levels. Critical to such a system are valid measures that permit fair comparisons. Indeed, generalization of randomized controlled trials to larger populations for performance measurement is a complex process that invariably involves judgment of the health benefit of the proposed measure as well as technical issues. Such factors include importance, scientific evidence, reproducibility, validity, precision, specification (including inclusion and exclusion criteria for the measure denominator), and feasibility in practice. The validity of methods measurement development, and adoption must be transparent. Transparency has been defined as “a process by which information about existing conditions, decisions and actions is made accessible, visible and understandable.”1 One concern is that in the rush to value-based purchasing, the views into the process by which measures are vetted are opaque, rather than transparent.