A 68-year-old woman underwent stereotactic biopsy of a small cluster of calcifications. The post-biopsy mammograms showed the biopsy-marking clip to be located correctly at the biopsy site. Follow-up mammograms 1 year later showed that the clip migrated to another quadrant of the breast. Findings in this case demonstrate that at long-term follow-up a biopsy-marking clip may not be accurately marking the biopsy site.