Since in the treatment of advanced breast cancer chemotherapy and the various hormonal manipulations seem recently to have reached a plateau of effectiveness when used alone, it is widely assumed that the combination of both treatment modalities could improve therapeutic results. The outcome is reported of a study encompassing 109 pre- and 297 postmenopausal evaluable cases with previously untreated metastatic breast cancer. The patients were randomized either to a concurrent chemo/hormonotherapy or to the hormonal treatment alone, chemotherapy being delayed until the occurrence of tumor progression. All patients were further randomized to 3 chemotherapy regimens (LMFP, LMP/FVP, LMFP/ADM) representing three different degrees of intensity. Pre-menopausal patients tend to live longer with the concurrent combination of both modalities, whereas postmenopausal patients fare better when chemotherapy is delayed until the occurrence of tumor progression with hormonotherapy alone. However, the differences in survival are statistically significant only in postmenopausal patients with a less aggressive tumor ("low-risk"). The more aggressive cytotoxic combinations elicit higher response rates than "minimal chemotherapy", but the differences translate only marginally into different survivals. These findings are discussed with regard in particular to their importance in establishing widely acceptable therapeutic rules for the treatment of advanced breast cancer.