The correlation between angiographic tumor blushing and underlying pathologic factors was studied. Twenty female patients with breast cancer were divided into three groups according to the degree of tumor blushing. Primary tumors were divided into three areas: marginal, central and intermediate areas. In each area, the number of blood vessels per 10(4) mu 2 was randomly counted in 10 fields and a mean value of vessels was compared among the three groups. It was found that the following pathologic findings were significantly related to strong angiographic staining: (i) well-circumscribed border; (ii) large tumor nest; (iii) severe inflammatory cell infiltration; (iv) mild stromal fibrosis; and (v) absence of lymph node metastasis. The mean value of blood vessels in the strongly positive group was significantly increased in the overall and the intermediate areas. The density of the vessels in the intermediate area was thus thought to be responsible for the tumor blushing.