In this study the possibility of classifying carcinoma in situ and normal specimens by measuring normal-appearing intermediate cells was explored. Twenty-five histologically verified carcinoma in situ specimens and 99 normal specimens, matched with the abnormal specimens for age and use or nonuse of an oral hormonal contraceptive, were examined. The smears were monolayer preparations stained with Thionin-Feulgen Congo red. Twenty-one nuclear features were measured. A discrimination among the experimental groups could be made on the basis of the relationship between two features, area and average optical density (AOD). A regression of AOD on area for each smear was performed. The correlation, coefficient of variation, slope, intercept, as well as the mean of the AOD level and the age of the subject were used in a discriminant analysis. This resulted in a smear classification with a false-positive rate of 14% and a missed-positive rate of 32%. When contraceptive use was taken into account the overall classification was improved with a false-positive rate of 12% and a missed-positive rate of 20%.