BACKGROUND. The National Cancer Data Base (NCDB), a joint project of the American College of Surgeons Commission on Cancer and the American Cancer Society, is a cancer management and outcome data base for health care organizations. It provides a comparative summary of patients care that is used by participating hospitals and communities for self-assessment. The most current (1995) data are described herein. METHODS. Since 1989, seven calls for data have been issued, yielding reports on a total of 240,031 breast carcinoma patients for the years included in this analysis. A total of 1849 hospital cancer registries responded to at least 1 of the calls for data. RESULTS. A continuous improvement in care was reported. By 1995, 45.8% (nearly one-half) of breast carcinoma patients were diagnosed early as Stage 0 or I, and early stage patients (Stage 0 or I) were most often treated with partial mastectomy (in 58% of cases). Favorable 10-year relative survival rates for Stage 0 (95%) and Stage I (88%) breast carcinoma patients were reported. Patients who were presumed to be Stage I and were not selected for axillary dissection had poorer survival. Survival differences were reported for different treatment groups within individual stage strata. Over the 10- year observation period, fewer patients from lower-income neighborhoods were diagnosed with early stage breast carcinoma. In general, the annual relative survival rate remained constant over the 10-year observation period (with no plateau after 5 years) within each stage and for all stages combined. CONCLUSIONS. Improvements in diagnosis and treatment during the period 1985- 1995 were demonstrated by these data. The NCDB breast carcinoma data are appropriate norms for normal quality assurance purposes, such as those specified by the Standards of the Commission on Cancer published by the American College of Surgeons Commissions on Cancer. Cancer committees and other clinicians working within the hospital setting should assess and compare stage distribution, stage specific treatment patterns, and the correlations between the outcomes of patients and both disease stage and treatment.