A new technique is described for image guided percutaneous diagnostic excision biopsy of non-palpable mammographically detected breast lesions. This method involves insertion of a localizing guide wire under stereotactic guidance followed by insertion of the 15 mm diameter biopsy device which is positioned within the breast immediately proximal to the target lesion. A cylindrical cannula is advanced over the lesion which is then separated from the surrounding breast tissue by deploying a garrote wire at the distal end of the cannula. The biopsy device is then removed with the target lesion contained within the cannula. The mammographic lesion is excised without removing any excess adjacent breast tissue, and in one piece, so allowing histological examination of the whole lesion. The experience of the first three cases is described with imaging and histological correlation.