The operations of any portion of the healthcare delivery system, eg, ambulatory care, the consultation and referral process, or hospital care, are critically dependent upon their control systems. The quality of health care produced by the system and its components is also subject to "control." One of the regulatory mechanisms involves performance measures. The development of good measures of quality is a complex and dynamic process. Within endocrinology, most measures have addressed diabetes care and most quality measurement in diabetes has focused on the ambulatory setting and mainly includes measures of process and intermediate outcomes. This review addresses quality and performance measures for diabetes, their development, characteristics, use, misuse, and future prospects.