Adjuvant systemic therapy has been shown to reduce relapses in treated women and to prolong their survival. This is true for all studied subpopulations. Multidrug chemotherapy for the duration of 6 months for the premenopausal patients, and tamoxifen or short-term chemotherapy with long-term tamoxifen for the postmenopausal patients represent the treatments of choice to reduce the risk of relapse. Some of the high priority questions relate to i) the definition of a population for which the risk of relapse is low enough to avoid the use of systemic adjuvant therapy, and ii) the definition of an optimal way of using available adjuvant therapies. These might find answers from ongoing research. The modest but real improvement of the prognosis in operable breast cancer was exclusively obtained only by means of clinical trials, and it is mandatory that participation in programs of clinical research becomes medically and socially the treatment of choice.