Despite a shift in care delivery from inpatient to ambulatory care, performance measurement efforts for the different levels in ambulatory care settings such as individual physicians, individual clinics and physician organizations have not been widely instituted in the United States (U.S.). The Health Plan Employer Data and Information Set (HEDIS®), the most widely used performance measurement set in the U.S., includes a number of measures that evaluate preventive and chronic care provided in ambulatory care facilities. While HEDIS® has made important contributions to the tracking of ambulatory care quality, it is becoming increasingly apparent that the measurement set could be improved by providing quality of care information at the levels of greatest interest to consumers and purchasers of care, namely for individual physicians, clinics and physician organizations. This article focuses on the improvement opportunities for quality performance measurement systems in ambulatory care. Specific challenges to creating a sustainable performance measurement system at the level of physician organizations, such as defining the purpose of the system, the accountability logic, information and reporting needs and mechanisms for sustainable implementation, are discussed.