Although the majority of patients with breast cancer have clinically negative axillary nodes at preoperative assessment, around 15-20% of these women will have metastatic disease within the lymph nodes at operative sentinel node biopsy, and additional selective treatment to the axilla might be required. Local treatment to the axilla can include axillary node clearance or axillary radiotherapy. The recent results of the American College of Surgeons Oncology Group Z0011 trial suggested that some women would be safe from recurrence without further axillary treatment if they have less than three involved sentinel nodes, with no extracapsular spread. We review the evidence base for management of the axilla after detection of a positive sentinel node, discuss the evidence for why micrometastatic disease requires systemic but not axillary therapy, and present data suggesting that axillary irradiation for macrometastases gives equivalent control to axillary node clearance, but causes less morbidity such as lymphoedema. Ongoing trials will confirm whether any further therapy can be omitted for all patients with low volume, sentinel-node macrometastases.