Breast cancer multifocality was studied in mastectomy specimens by correlating specimen mammography and histologic techniques. Twenty five mastectomy specimens in 23 patients with breast cancer were included. Of 25 specimens, 7 cases were ductal carcinoma in situ, one was invasive lobular carcinoma and others were invasive ductal carcinoma. Multifocal cancer foci were present in 5(29%) mastectomy specimens in 17 patients with invasive ductal carcinoma. Forty five percent of mulitifocal lesions were located within 2 cm from the tumor margin and 78% were located within 5 cm. Histologic features of multifocal tumors were intraductal cancers except one area of invasive cancer. Topographical analysis showed that all multifocal tumor foci were located in same or adjacent quadrants. Tumor size was not related with multifocality. Three out of seven cases of ductal carcinoma in situ had multifocal cancer foci. We concluded this results may be one of the theoretical basis of rational appraoch to the con 'servative treatment such as quadrantectomy of breast cancer.