The National Cancer Data Base (NCDB) is a nationwide outcomes database for oncology presently including 1,600 hospitals in 50 states. Half of all U.S. cancer cases are accessioned annually. It is important for U.S. clinicians and health information management professionals to become familiar with the NCDB to increase the usefulness of this comparative database in their hospital quality assurance programs. The NCDB's unique characteristics include its implementation by clinicians, its provision of access to data from hospitals participating in the Approvals Program of the Commission on Cancer, and its affiliation with a 2,200-member national physician network. The NCDB annual data are augmented by patient care evaluation studies, which provide a capability for cross-sectional surveys with an expanded data set. The NCDB has participated in the significant data standardization effort for U.S. cancer registries. The procedures used maintain confidentiality of the patient, physician, and participating hospital, and physical access to the data files is limited. The three primary products of the NCDB are hospital comparative reports, state and local reports, and scientific reports.