To evaluate the feasibility of adjuvant chemotherapy, we analyzed the toxicities of chemotherapy for primary breast cancer in Japanese women, Since the opening of the National Cancer Center Hospital East, 180 female breast cancer patients have received adjuvant chemotherapy or chemo-hormonal therapy following surgical treatment between June 1992 and December 1995. On the basis of informed consent about prognosis and adjuvant therapy, most patients decided to choose the type of cytotoxic chemotherapy themselves. Adjuvant chemotherapy consisted of oral fluoropyrimidine compounds (OFP), cyclophosphamide + adriamycin +/- 5-fluorouracil [CA(F)] or cyclophosphamide + methotrexate + 5-fluorouracil (CMF), Toxicity was determined using the Toxicity Grading Criteria of the Japan Clinical Oncology Group (JCOG), Sixty-six patients received OFP, 59 CA(F) and the rest 55 CMF, The toxicity grading of leukocytes and neutrophils was significantly higher in patients treated with CA(F) or CMF than in those treated with OFP. Similar results were also seen relating to the toxicity of nausea/vomiting and alopecia, There was no statistical difference in the toxicity grading of hemoglobin, glutamic oxaloacetic transaminase/glutamic pyruvic transaminase (GOT/GPT) and stomatitis/gastritis between the three groups of patients, Interestingly, the number of patients that were forced to discontinue chemotherapy was higher in those receiving OFP than in those receiving CA(F) or CMF, Cytotoxic chemotherapy of CA(F) or CMF results in greater toxicity than OFP, but is tolerated and feasible in the adjuvant setting used in Japanese breast cancer patients from the viewpoint of toxicities by anticancer chemotherapy.