Measuring the quality of health care delivery is one of the most critical challenges facing US health care. Performance measurement can be used to track the quality of care that health plans and medical groups deliver, but effective performance measurement requires timely access to detailed and accurate data. In 1996, the National Committee for Quality Assurance (NCQA) commissioned a report to learn what actions would improve health plans' capacity to electronically report performance data for the Health Plan Employer Data and Information Set (HEDIS). Tracking clinical performance will require not just clinical data stored in information systems, but an integrated health information framework. Seven features are essential to this framework: (1) it specifies data elements; (2) it establishes linkage capability among data elements and records; (3) it standardizes the element definitions; (4) it is automated to the greatest possible extent; (5) it specifies procedures for continually assessing data quality; (6) it maintains strict controls for protecting security and confidentiality of the data; and (7) it specifies protocols for sharing data across institutions under appropriate and well-defined circumstances. Health plans should anticipate the use of computerized patient records and prepare their data management for an information framework by (1) expanding and improving the capture and use of currently available data; (2) creating an environment that rewards the automation of data; (3) improving the quality of currently automated data; (4) implementing national standards; (5) improving clinical data management practices; (6) establishing a clear commitment to protecting the confidentiality of enrollee information; and (7) careful capital planning. Health care purchasers can provide the impetus for implementing the information framework if they demand detailed, accurate data on the quality of care.