Medicare RBRVS has become widely used as a standard for physician fee scales by both traditional health insurance plans and managed care organizations. There are significant variations in the way RBRVS has been adapted by these private payers. These variations, when combined with changes Medicare has made to the underlying components of RBRVS, may result in unintended and unexpected increases in physician payments. To avoid surprises, payers using RBRVS-based fee scales need to carefully evaluate the overall impact of annual RBRVS modifications on their delivery systems.