In the breast cancer adjuvant therapy setting, the critical issue to consider in treatment decision-making is the tradeoff between quality and quantity of life. The toxicities of adjuvant therapies, both acute and late, must be balanced against the potential benefits of delayed recurrence and improved survival. The question should be addressed concerning when quality-of-life assessment is relevant in the adjuvant setting. Such assessments can inform patients about what to expect from their treatment, describe quality-of-life differences between treatments, provide an additional baseline measure with potential prognostic significance, inform clinicians about their patients' experiences with toxicities, indicate situations in which psychosocial interventions might be useful, and document patient adaptation to diagnosis and treatment. The relevance of quality-of-life assessment in the adjuvant setting can be illustrated by investigating one of the most controversial questions of today: When should chemotherapy be added to tamoxifen for postmenopausal patients? Data from the International Breast Cancer Study Group (IBCSG) Trial VII showed that adding 3 months of CMF (cyclophosphamide 100 mg/m2 orally days 1-14; methotrexate 40 mg/m2 i.v. days 1, 8; fluorouracil 600 mg/m2 i.v. days 1, 8; repeated every 28 days) to tamoxifen significantly improved disease-free survival compared with tamoxifen alone. The Quality-adjusted Time Without Symptoms of disease or Toxicity of treatment (QTWiST) method was used to compare the adjuvant therapies with respect to quality-adjusted survival. The analysis indicated that the decision to use adjuvant chemotherapy in this setting should be based on patient preferences concerning the relative importance of treatment toxicity versus disease recurrence.