PURPOSE: Breast cancer has been the most prevalent cancer among Korean women since 2001, yet the nationwide survival data for cancer patients has not been examined. The purpose of the present study is to analyze the survival rate of breast cancer patients in Korea using the nationwide data in the cancer registry. METHODS: The Korean Breast Cancer Society (KBCS) has been collaborating with the Korean Central Cancer Registry (KCCR) to improve the completeness and validity of the breast cancer registry and the mortality data. Data from 1993 to 2002 from KBCS? on-line registry and the KCCR were merged, and a total of 49,174 patients were included for survival analysis. RESULTS: The five-year observed survival rate and the relative survival rate were 81.2 and 83.2%, respectively, for all patients (80.3 and 82.3%, respectively, for the patients with invasive cancer). The five-year survival rates increased steadily from 1993 to 2002; during the period 1993-1997, the 5-year survival rate was 77.6%, and it was 82.6% during the period 1998-2002, representing an increase of 5%. Both early detection and progress in treatment might have contributed to the increased survival rates. The survival rates are highly dependent on the stage at the time of diagnosis. The five-year observed survival rates were 99.0% for stage 0, 95.6% for stage I, 88.6% for stage II, 64.2% for stage III, and 28.2% for stage IV. No difference in survival according to gender was observed. Patients younger than 35 years of age at diagnosis had a lower rate of survival compared with the older patients. The survival rates of the breast-conserving surgery group was better than that of the mastectomy group; this result was associated with findings that the breast-conserving surgery group had a greater proportion of early cancers and patients with a positive estrogen receptor status and a smaller proportion patients with c-erbB2 overexpression compared with the mastectomy group. The breast-conserving surgery group had smaller tumor sizes and fewer lymph node metastases than that of the mastectomy group in the same stage. The survival rates of invasive cancer with predominant intraductal carcinoma, mucinous carcinoma, medullary carcinoma, and papillary carcinoma were more favorable, whereas inflammatory carcinoma showed poorer survival compared with that of the invasive NOS type. The survival rate of hormone receptor-positive patients was more favorable than that of hormone receptor-negative patients. CONCLUSION: The present study calculated the nationwide survival rates of Korean breast cancer patients for the first time. The survival rates of Korean breast cancer patients were similar to those of the United States, Europe, and Japan, suggesting the improvement in treatment as well as early detection of breast cancer. Further analysis of the long-term survival and a nationwide collaborative study should be performed to estimate the survival trend of Korean breast cancer patients.