To assess chemoendocrine therapy in the adjuvant treatment of patients with Stage II or III breast cancer, 228 patients were enrolled in a 12-month trial period from January 1982 to January 1983. One hundred ninety evaluable patients were followed up for five years. The regimen in this trial consisted of intravenous administration of 13 mg of mitomycin C per m2 during the operation and 6.5 mg of the same drug per m2 on the first day, and oral administration of 600 mg of tegafur per m2 alone or supplemented with 13 mg of tamoxifen per m2 for two years. No survival advantage was observed with addition of tamoxifen to tegafur in terms of five-year survival (88.7% vs 86.6% for Stage II and 69.9% vs 82.2% for Stage III). However, there was a significant prolongation of relapse-free survival among patients receiving tegafur and tamoxifen as compared with those who received tegafur alone: 72.9% vs 55.8% (p = 0.098 in the logrank test).