Adjuvant chemotherapy with cyclophosphamide, 5-fluorouracil and methotrexate (CMF)-induced permanent ovarian suppression in 47 of 77 (61%) premenopausal patients with axillary node positive breast cancer. After a median observation time of 37 months the relapse-free and overall survival times were significantly longer for patients with permanent amenorrhoea. A strongly positive correlation between CMF-induced amenorrhoea and age of the patients, as well as between age and the tumour PgR status, was found. The induction of ovarian suppression predominantly occurs in patients with PgR positive tumours and may add an endocrine effect to the cytotoxic action of adjuvant chemotherapy in this particular group of older premenopausal women.