In breast cancer patients with negative sentinel node biopsy (SNB), surveillance of the unremoved nodes is recommended. Clinical examination has poor sensitivity. The aim of this study was to evaluate the role of axillary ultrasound scan (AUS) in the follow-up of these patients. AUS was performed every 12 months in a series of 165 patients with negative SNB. During the follow-up (median 45.6 months), in 154 patients, the AUS was carried out as a routine examination and in three cases (1.9%) it showed suspicious nodes, which underwent core biopsy. No evidence of axillary recurrence was found. Conversely, in 11 patients, AUS was performed to clarify a palpable lymphadenopathy; none of them was suspicious at US. We conclude that routine AUS to follow-up patients who have had a negative SNB is unnecessary. However, AUS may be useful in the presence of palpable nodes, to select those patients who do not require biopsy.