METHODS. Personal information and clinical and pathological records were collected for 178 of 310 new cases of breast cancer in 1991 Cancer Registry of Taiwan. RESULTS. Among the subjects studied, 89.3% of the breast cancers were found incidentally. Delayed treatment, doctor shopping, and taking traditional medicine were common. Only 19.7% of the tumors were not more than 2 cm in diameter when the patients received treatment. The most important factors related to tumor size at treatment were occupation, family economic status, and action after detection. Those who were employed, had higher family economic status, and saw a doctor immediately after the tumor was detected were likely to have smaller (< or = 2 cm) tumors at treatment. The application of screening methods, however, did not show any significant relationship. The authors suggested implementing a breast self-examination health education program, evaluating cost-benefits of different screening methods, and setting up a breast cancer screening model that can meet the needs of Taiwanese women.