Abstract: Objective To evaluate the curative effect and adverse effects of three-dimensional conformal radiotherapy (3D-CRT) for breast cancer patients with brain metastases. Methods Clinical data about 47 breast cancer patients with brain metastases admitted to The Military General Hospital of Beijing PLA and Chinese PLA General Hospital from May 1995 to October 2010 who underwent the whole brain radio therapy (WBRT) were retrospectively analyzed. The doses of WBRT was 50 Gy in 2 Gy fractions, or 40 Gy in 2 Gy fractions with simultaneous integrated boost to multiple brain metastases (DT 60 Gy in 3 Gy fractions). Part of the patients underwent stereotactic radiotherapy with 10-24 Gy/1-3 F. The curative effect and adverse reactions were evaluated for one to three months after radiotherapy. Results All patients were followed up for 2-49 months. CR was observed in 5 cases (10.6%), PR in 26 cases (55.3%), SD in 13 cases (27.7%), PD in 3 cases (6.4%), and the clinical response rate was 66.0%. 1, 2 and 3 years survival rates of brain metastases to death were 53.2%, 25.5% and 2.1% respectively, and the median survival time was 13 months. The main adverse reactions were radiation-induced cerebral edema, alopecia, tympanitis, hearing loss, dermoreaction, acratia, marrow suppression, impaired memory and Ⅲ-Ⅳ nervous system side effects. The univariate analysis showed that KPS (＜ 50 and ≥60) (t=4.37, P=0.00) was a significant prognostic factor of overall survival time. The mutivariate analysis showed that KPS (u=3.05, P=0.00), AJCC stage (u=2.09, P=0.04), brain metastasis number (＜ 3 and ≥3) (u=1.94, P=0.05) and intracranial progress (u=2.21, P=0.03) were significant prognostic factors of overall survival time. Conclusion 3D-CRT can improve the local control rate of breast cancer patients with brain metastases, and prolong the survival time with few adverse effects. It is safe for patients treating with whole brain radiotherapy (DT 40 Gy, 2 Gy/fraction). Patients with good KPS, early stage, few brain metastasis number and occuring intracranial progress later may have longer overall survival time.