DNA ploidy abnormalities of 21 archival human esophageal intraepithelial neoplasia samples were assessed, using image cytometry of deparaffinized samples, with reference to invasive squamous cell carcinoma and corresponding uninvolved squamous epithelium. Cytometric parameters investigated were proportion of G0G1 aneuploid cell population, histogram typing, proportion of G0G1 diploid nuclei, coefficient of variation, mean DNA content, crude 5c exceeding proportion, 2c deviation index, malignancy index and grade, and entropy. The distributions of the above parameters were compared using the paired t test and Fisher's exact test. Among 10 parameters used, Auer typing of DNA histograms, crude 5c exceeding rate, 2c deviation index and malignancy grade according to Böcking allowed discrimination between uninvolved epithelium and invasive squamous cell carcinoma as well as intraepithelial neoplasia. In particular, the distribution of 2c deviation index in the uninvolved epithelium did not overlap that of intraepithelial and invasive carcinomas. The above four parameters, however, were unable to discriminate intraepithelial neoplasia from invasive carcinoma.