Biopsy of the impalpable breast lesion is an increasing part of the surgical workload as a result of the National Breast Cancer Screening Programme. A specimen mount card has been described to orientate such specimens in three dimensions prior to radiological and pathological examination. Experience with 243 biopsies in this unit has shown it to be a useful aid in determining completeness of excision. It may also be used as a guide to further surgery when excision is incomplete and breast conservation is the treatment option of choice.