Thirty-nine patients with locally advanced breast cancer (T3b-4, N1-3 or inflammatory carcinoma) received 3 cycles of induction chemotherapy with estrogenic recruitment before surgery. The therapeutic regimen consisted of diethylstilbestrol (DES) orally on days 1-3, 5-Fluorouracil + Doxorubicin + Cyclophosphamide on day 4 q 21 days (DES-FAC). After surgery 6 additional cycles of chemotherapy (3 DES-FAC alternating with 3 DES-CMF with Methotrexate + F and C as in FAC) were administered. The objective response rate was 71.8% with 15.4% CR, and 56.4% PR; after surgery 36/39 (92.3%) patients were rendered disease-free. So far, 13 of 26 patients in stage IIIb have relapsed (9 of 13 with inflammatory carcinomas). Three-year survival and progression-free survival are 60% and 53.5%, respectively. Twenty-three of the 39 patients were subjected to serial tumor biopsies during the first DES-FAC regimen to allow for tumor-cell kinetic studies during DES and chemotherapy. A significant estrogenic recruitment occurred in 16 patients (69.6%), irrespective of estrogen-receptor status. At surgery, 3-4 weeks after induction chemotherapy, tumor proliferative activity was significantly depressed in comparison to basal values. These results indicate that breast cancer cells can be recruited in vivo with DES and that chemotherapy following estrogenic stimulation is effective and feasible with acceptable toxicity.