The value of dipping cervical cone biopsy specimens in iodine (the Schiller test) as a method of deciding which areas should be selected for histological examination was assessed. Schiller positive and negative areas were recorded in macroscopic specimen images from fifty specimens of cervix. The results were compared with the histological presence or absence of cervical intraepithelial neoplasia (CIN) or invasive malignancy. In 84% of cases the test was a reliable means of predicting the presence or absence of squamous CIN; in two cases it was positive in association with endocervical adenocarcinoma in situ. A false positive and false negative Schiller's test was present in three cases (6%) each. Had this method been adopted as the sole means of selecting blocks for histological examination the areas of CIN would have been missed in 6% of cases. Therefore it is not a sound alternative to the submission of all tissue for histological examination.