Between 1985 and 1988, the effect of using ftorafur (FT) or PSK (an immunotherapy agent) in combination with the conventional postoperative adjuvant therapy using mitomycin (MMC) plus tamoxifen (TAM) was assessed in stage II, oestrogen receptor-positive (ER+) breast cancer patients. Furthermore, in ER- breast cancer stage II patients, the effects of postoperative adjuvant therapy using MMC plus FT were compared with the effects of postoperative adjuvant therapy using MMC plus PSK. Patients had primary stage II breast cancer and had undergone total mastectomy plus axillary dissection or more radical surgery. On the day of surgery, MMC (13 mg/m2) was administered intravenously. Then, ER+ patients received one of three regimens of drug therapy, starting 2 weeks after surgery: regimen A (daily oral treatment with 30 mg of TAM), regimen B (daily oral treatment with 30 mg of TAM and 600 mg of FT) or regimen C (daily oral treatment with 30 mg of TAM and 3 g of PSK) [corrected]. ER- patients received either regimen D (daily oral treatment with 600 mg of FT) or regimen E (daily oral treatment with 3 g of PSK), starting 2 weeks after surgery. Of the 540 ER+ patients registered, 525 were evaluated. The 5-year overall survival rate for ER+ patients was higher for patients who received regimen B (94.2%) than for those who received regimen A (86.9%) or regimen C (89.9%) (P = 0.063). The 5-year relapse-free survival rate was higher for regimen B (88.9%) than for regimen A (78.6%) and regimen C (77.2%) (P = 0.010). Stratified analysis revealed better results with the FT-combined therapy in patients positive for lymph node metastasis and premenopausal patients. These results indicate the effectiveness of using FT in combination with TAM. Of the 376 ER- patients registered, 364 were evaluated. The 5-year overall and relapse-free survival rate for ER- patients did not differ significantly between patients who received regimen D and those who received regimen E.