Comparisons between the effects exerted by adjuvant cyclophosphamide, methotrexate and 5-fluorouracil (CMF)-based polychemotherapy and endocrine treatment in premenopausal breast cancer patients are validly drawn in the presence of steroid hormone receptor responsiveness. First, ovarian ablation still remains to show activity compared with chemotherapy in large patient groups. Second, tamoxifen is at least as active in this cohort and, by comparison, produces a significant effect in mortality reduction. Third, induction of reversible amenorrhoea by LHRH analogue administration has shown comparable effects in terms of recurrence-free survival. Finally, recent European investigations have indicated significant recurrence reductions with LHRH analogue-tamoxifen combination strategies. In conclusion, various endocrine treatment modalities have been substantiated as equiefficient to polychemotherapy. Tamoxifen added to a LHRH analogue further diminishes the recurrence rates and now appears to be a valid treatment alternative. We argue that selection of adjuvant systemic therapy for premenopausal breast cancer patients be increasingly guided by knowledge of the steroid hormone receptor levels.