OBJECTIVES: This study was performed to assess the risk factors, histologic and clinical features of breast cancer in postmenopausal women receiving hormone therapy (HT). METHODS: We evaluated 40 breast cancer patients who received HT due to postmenopausal symptoms by reviewing their medical charts at Pusan National University Hospital. Research variables, including patients' history, type and duration of received HT, moment of cancer debut after starting HT, radiological characteristics of breast cancer stage, histologic type, tumor size, grade, lymph node metastasis, estrogen and progesterone receptor status and 5-year survival were investigated. RESULTS: In the risk factors of breast cancer patients, only one patient had familial history of breast cancer. No patient had smoking history. The average body mass index (BMI) was 23.2 kg/m2. Twelve patients (30%) had estrogen only therapy, 13 patients (32.5%) had combined estrogen and progesterone therapy, 10 patients (25%) had tibolone therapy and the others consecutively received combination therapy of the above regimens. The mean duration of treatment was 31 +/- 27.9 months (range 0.4-115 months). In the distribution of the cancer debut after starting HT, in 4 cases (10%) was within 1 year, 5 cases (12.5%) within 1-2 years, 10 cases (25%) within 2-3 years, 4 cases (10%) within 3-4 years, 1 case (2.5%) within 4-5 years, and 16 cases (40%) within more than 5 years. The average diameter of tumor size was 1.7 cm. In 92.5% of cases, the tumor was of ductal type. Tumor stage 0 and 1 appeared in 66% and grade I was present in 38% of investigated cases. Hormone receptor-positive breast cancers were 85% and 70% of patients had negative lymph node metastases. The 5-year survival rate was 92%. CONCLUSION: The breast cancers which emerged during HT in postmenopausal women had hormone receptor-positive tendency. The size and stage of these breast cancers were shown as small and low, and represented low-grade differentiation. Recurrences of disease were uncommon and we found favorable 5-year survival rates and good prognosis.