A third series of randomized tests was undertaken to evaluate the efficacy of postoperative adjuvant hormone therapy (tamoxifen, diethylstilbestrol, orimethen amino glutethymide) in breast cancer patients. Tamoxifen was studied in 176 patients with T1-2N0M0 tumors. Five-year recurrence-free survival was registered in 85.2% of menopausal patients treated with tamoxifen versus 71.1% in control (P < 0.05). Five-year recurrence-free survival in menopausal females with breast tumors, stage IIb, was 71.1% among those treated with diethylstilbestrol and as low as 57.4% in the tamoxifen group (P < 0.05). Untoward side-effect incidence was much higher in the diethylstilbestrol group (30.4%) as compared with tamoxifen (3.5%). No significant difference was found for the relationship between orimethen and tamoxifen treatment with respect to 5-year survival and recurrence-free survival.