AIM--To determine whether sampling the anterior and posterior cervical lips in hysterectomy specimens provides the best opportunity for detecting unsuspected cervical intraepithelial neoplasia (CIN). METHODS--The frequency with which CIN was identified at a range of positions on the anterior and posterior lips and left and right lateral aspects of the cervix was assessed in 100 cone biopsy specimens. RESULTS--CIN affected one or other cervical lip in all 100 cases studied and involved the midline positions (12 and 6 o'clock) in 94. The lateral edges of the cervical canal were also involved in 38 cases. CONCLUSION--CIN is more likely to be identified on the anterior and posterior lips than on the lateral aspect of the cervical os. The findings support the continuation of the established practice of taking blocks from the midline in these areas.