The standard technique for surgical excision of mammographically detected, ultrasound invisible, non-palpable breast lesions is by pre-operative stereotactic guidewire localization (SGL). Disadvantages of SGL include patient discomfort, ionizing radiation, the requirement for more staff and longer procedure time. Ultrasound visible clips are used for localisation after vacuum-assisted core biopsies (VACB) but clip migration and visibility are problems. Post-VACB, the biopsy cavity fills with haematoma, which is ultrasonographi-cally visible and can be used as a 'marker' for guidewire localisation. Centres in America have successfully used ultrasound intraoperatively to identify the post-biopsy haematoma and guide surgical excision; but no centres have attempted to use ultrasound pre-operatively to locate the post-biopsy haematoma and direct guidewire placement. We aim to describe this new technique of haematoma-directed ultrasound guidewire localisation (HUGL) and compare its accuracy with SGL.