The National Institutes of Health, USA sponsored a Consensus Development Conference on November 1-3, 2000 to review several major questions regarding the adjuvant treatment of breast cancer. A non-governmental group of oncology experts was selected to review clinical trial data and judge the evidence presented by 33 breast cancer researchers. Their conclusions resulted in the following recommendations: (1) Prognostic factors critical for determining risk of recurrence are age, axillary lymph node status, tumor size, histologic type and grade and hormone receptor status. (2) Tamoxifen, administered for 5 years, significantly improves long-term survival for women of all age groups with hormone receptor-positive tumors. Ovarian ablation also prolongs survival in premenopausal women. (3) Multi-agent chemotherapy of 4-6 months duration is associated with an improvement in survival in both hormone receptor-positive and -negative tumors. Anthracycline-containing regimens offer the greatest survival advantage. The role of taxanes is uncertain but they may be useful in selected patients with node-positive tumors. Women with small, node-negative tumors, women over age 70, and those with tumors of favorable histologic subtype (mucinous or tubular) may not require chemotherapy. (4) Adjuvant radiotherapy to the regional lymph nodes and chest wall following mastectomy is indicated for women with 4 or more axillary nodes. (5) Physicians should employ effective visual aids to help them present a complete and balanced view of the absolute benefits versus the side-effects of adjuvant treatments. Important avenues of future research were also discussed and suggestions were made.