AIM: To determine the impact of preoperative axillary ultrasound staging in a screen-detected breast cancer population. MATERIALS AND METHODS: Ultrasound and needle biopsy staging results alongside reference standard sentinel lymph node biopsy and axillary lymph node dissection were extracted retrospectively from the unit's computer records between 1 April 2008 and 31 March 2015. Axillary staging was compared with final histopathology and treatment. RESULTS: Of the 215,661 screening examinations performed, 780 invasive cancers were diagnosed, which had preoperative axillary staging data, of which 162 (20.7%) were node positive. Thirty-six (4.6%) had a heavy nodal burden (three or more nodes). Ninety (11.5%) had an abnormal axillary ultrasound and axillary biopsy of which 54 were positive for cancer (33.3% of the node positive cases) and triaged to axillary lymph node dissection avoiding a sentinel lymph node biopsy. Of these 22 (40.7%) had neoadjuvant treatment, and 32 (59.3%) proceeded directly to axillary lymph node dissection. The sensitivity of axillary ultrasound and biopsy to detect women with a heavy nodal burden (three or more nodes) was 41.7% (15 of 36); however, 17 (53%) of the 32 women with a positive axillary biopsy had a low burden of axillary disease (two or fewer positive nodes) at axillary lymph node dissection, the mean number of nodes obtained was 14.6. CONCLUSION: Significant numbers of women are being potentially overtreated or denied entry into positive sentinel node: adjuvant therapy only versus adjuvant therapy and clearance or axillary radiotherapy (POSNOC) because of routine preoperative axillary staging.