PURPOSE: To evaluate changes seen on mammograms obtained after large-core stereotaxic biopsy of the breast. MATERIALS AND METHODS: Twenty-seven patients underwent stereotaxic breast biopsy performed with large-core, 14-gauge needles. At least five core samples were obtained from each lesion. The mammograms obtained before biopsy were compared with those obtained 6 months later in the 24 patients in whom follow-up was performed. RESULTS: The only changes seen on the postbiopsy mammograms were due to tissue sampling (ie, fewer microcalcifications or defects were seen in areas of lesions from which tissue had been extracted). CONCLUSION: Large-core needle biopsy of the breast does not produce change or deformity that can be recognized on mammograms. Parenchymal scarring, architectural distortion, fat necrosis, or other identifiable changes seen after surgical biopsy of the breast are not seen after large-core, stereotaxic breast biopsy.