- Serial respiratory function tests were performed in nine women after mastectomy due to breast cancer, prior to and during six adjuvant chemotherapy treatments with CMF (cyclophosphamide, methotrexate and 5-fluorouracil). None of them had ever had respiratory diseases and during the period of treatment all were free of respiratory symptoms or signs. Vital capacity (VD) and total lung capacity (TLC) prior to the sixth treatment were significantly lower (p < 0.05) than prior to the first treatment. Forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1.0) also decreased significantly (p < 0.02) but the ratio between them did not change, nor did any other respiratory function measured. We conclude that the CMF combination causes a mild ventilatory disturbance which merits further investigation.