Experience with external quality assurance of managed care organizations has been gained in the United States since the 1990's. The leading organization in this respect is the National Committee for Quality Assurance (NCQA) a private, not-for-profit organization with the aim of improving the quality of health care by assessing and reporting on the quality of managed care organizations. The NCQA’s two complementary strategies are the accreditation of managed care organizations and performance measurement using a standardized set of measures of structure, process and outcomes of care (HEDIS). Use of this information by the various user groups and effects of the external quality assurance activities are described. If following the recent years’ changes in legislation an increased diversification of sickness funds takes place in Germany, e. g., through selective contracting with distinct groups of providers or health care delivery organizations, or through a widespread establishment of integrated care networks using managed care tools, then - complementary to the quality management within these organizations - measures of external quality assurance and an increased transparency of care should be implemented. These should allow monitoring the effects of managed care instruments on the quality of care and facilitate informed choices of sickness funds and provider networks by consumers. In developing such concepts it can be very helpful to evaluate the described instruments and the experience with their application.