Data on 368 patients with breast carcinomas measuring < or = 5 cm were analyzed to study the relationship between the prognostic factors and the flow indices measured by color Doppler ultrasound (US). Vascularity was detected by color Doppler US in 348 (94.6%) of the 368 breast tumors. Tumors without vascularity were significantly (p = 0.0001) smaller than the tumors with vascularity. There was a correlation between Vmax and tumor size. Postmenopausal women had greater values of RI, PI, and V(max). Tumors larger than 2 cm had significantly greater RI, V(max) and number of vessels as compared with the tumors smaller than 2 cm. RI was significantly greater in the nondiploid tumors than in the diploid tumors. RI > or = 0.7 was significantly associated with nondiploid carcinomas and SPF > or = 7%. Tumor size and Vmax significantly predicted axillary lymph node metastases.