OBJECTIVE: Sentinel node biopsy (SNB) is widely used to stage the axilla in breast cancer. We present 10-year follow-up of our single-institute trial designed to compare outcomes in patients who received no axillary dissection if the sentinel node was negative, with patients who received complete axillary dissection. METHODS: From March 1998 to December 1999, 516 patients with primary breast cancer up to 2 cm in pathologic diameter were randomized either to SNB plus complete axillary dissection (AD arm) or to SNB with axillary dissection only if the sentinel node contained metastases (SN arm). RESULTS: The 2 arms were well-balanced for number of sentinel nodes found, proportion of positive sentinel nodes, and all other tumor and patient characteristics. About 8 patients in the AD arm had false-negative SNs on histologic analysis: a similar number (8, 95% CI: 3-15) of patients with axillary involvement was expected in SN arm patients who did not receive axillary dissection; but only 2 cases of overt axillary metastasis occurred. There were 23 breast cancer-related events in the SN arm and 26 in the AD arm (log-rank, P = 0.52), while overall survival was greater in the SN arm (log-rank, P = 0.15). CONCLUSIONS: Preservation of healthy lymph nodes may have beneficial consequences. Axillary dissection should not be performed in breast cancer patients without first examining the sentinel node.