Adjuvant therapy with either chemotherapy or hormonal therapy offers statistically significant benefits for most subsets of women with breast cancer that in many cases outweigh the risks of treatment, but the potential benefit will vary from patient to patient and by modality of therapy. The absolute reduction in risk is proportional to the overall risk of relapse or death, so greater absolute benefit can be anticipated for those with a greater risk. Consensus recommendations provide a reasonable outline for initiating the discussion of adjuvant therapy, but treatment considerations must be individualized to take into account the patient's personal willingness to accept these weighed estimates of objective probabilities of benefit, toxicity, and risk. Many questions remain and will be answered only through the clinical trials process. Every patient with breast cancer should be given the opportunity to consider participation in a clinical trial when appropriate for both the sake of medical knowledge and the benefit of future patients.