BACKGROUND: In recent years many health care providers, physicians, hospitals, and managed care organizations have undergone significant reorganization in both delivery and financing systems. This has created new organizations called integrated or organized delivery systems. Sentara Health System (Norfolk, Va), one of these new integrated entities, developed a unified strategy for clinical process improvement for the entire organization. This system-wide approach had unanticipated problems and benefits. METHODS: The Sentara Health System created a team responsible for coordinating clinical process improvement activities across its hospitals and ambulatory physician sites. A steering committee directed this team to improve the organization and delivery of care for specific high-cost, high-volume, or problem-prone disease for physicians to manage. A standardized approach aimed at coordinating care across sites was the cornerstone of these activities. RESULTS: Significant improvements in patient outcomes and a concomitant decrease in costs of care were accomplished for multiple diseases and procedures. These projects uncovered unanticipated barriers to implementing improvement projects in a complex health care system which make implementing these activities far more difficult than for an individual hospital with its medical staff. CONCLUSION: Coordinating clinical improvement activities across multiple hospitals and other sites of care in a complex integrated delivery system serves important purposes in addition to improving patient care. These projects were an important cultural change agent to transform the individual components of the system into one that is capable of delivering care continuously across multiple sites. Standardization of care practices, policies, and procedures is considerably enhanced by coordinating these activities across the entire system.