The United States health care system is under tremendous pressure to cut costs while maintaining quality. One mechanism to reduce costs is managed care--a system with both risks and benefits for patients, providers, and payors, and one that requires large volumes of data to ensure optimal medical and financial decision-making. In this review, we describe the types of information needed by managed care systems, including medical outcome data (satisfaction, survival, quality of life, and complications) and financial data (costs and long-term resource utilization). From a provider's point of view, the customers for these data range from individual patients to large self-insured corporations, and we describe the data required for each potential customer. Finally, as a concrete example of how data can be collected and analyzed to improve a provider's competitiveness, we describe the Cedars-Sinai Medical Center cardiothoracic surgery database from a managed care perspective. The concepts presented are generalizable to other subspecialties, and will become more important in the increasingly competitive milieu of American health care.