It is very unusual for a malignant phyllodes tumor of breast to coexist with an intraductal carcinoma of the opposite side. We report herein such a 47-year-old woman in our hospital. For 20 years, she suffered from a palpable mass over of the left breast. In addition, at pre-operation survey, another lesion of the right breast was detected by sonography. Frozen sections from the biopsies of the bilateral tumors showed intraductal carcinoma of the right breast associated with a malignant phyllodes tumor of the left breast. The coexistence of tumors in bilateral breasts has been documented rarely in the past. The clinico-pathological features of phyllodes tumor and intraductal carcinoma are discussed and reviewed in this paper.