PURPOSE: Primary radiation therapy following breast-conserving surgery has been an accepted alternative to mastectomy during the past 2 decades. In this country, however, the practice of conservative therapy for early invasive breast cancer has not been generalized yet. The purpose of this report was to evaluate the results and complications of breast conservation therapy in Korean Cancer Center Hospital(KCCH) MATERIALS AND METHODS: From January 1987 to December 1989, 45 patietns with early breast cancer treated with conservative treatment in KCCH were studied retrospectively. Median follow up was 54 months(range, 4 to 82 months). All patients received partial mastectomy (biopsy, tumorectomy, or quadrantectomy) and radiation therapy. Twenty eight patients received axillary dissection. The breast was treated with two poosing tangential fields (total 50 Gy or 50.4 Gy in 5 weeks with daily target dose of 2 Gy or 1.8 Gy). Thirty patients received chemotherapy before and after radiotherapy. Eleven patients received hormonal therapy. RESULTS: Five-year survival rate, 5-year disease free survival rate and 5-year local control rate were 87.2%, 86.5% and 97.6%, respectively. Administration of systemic Therapy (chemotherapy or hormonal therapy) correlated with good prognosis but statistically not significant (0.05 < p < 0.01). The sever late complication rate was 8.9%. CONCLUSION: Primary radiation therapy following breast-conserving surgery for early breast cancer is an alternative treatment comparing to radical treatment. Long term follow-up and more patients collection is needed to evaluate the prognostic factor and cosmetic outcome.