DNA measurements performed with image cytometry in nuclei isolated from paraffin-embedded tissue of (pre)malignant lesions are described. DNA histograms are obtained in which one or more peaks are present, the latter representing one or more (pre)malignant cell populations. The DNA index [modal DNA peak value of the (pre)malignant cells divided by that of normal cells] can be computed and is comparable with that obtained with flow cytometry, a widely accepted technique to perform DNA cytometry. Quality of the histograms can be improved by eliminating the nonrelevant tissue in advance, and examples are shown of histograms of morphologically different regions in the same tissue. The use of DNA index in the clinical application on dysgeminomas of the ovary and small-cell lung cancer is discussed and its use for the characterization of cervical intraepithelial neoplasms grade III and metastases of small-cell carcinomas of the lung.