Cytophotometric analysis of cervical intraepithelial neoplasia grade I11 (CIN 111) was performed in 22 cytological smears (CS) and in 22 corresponding cytospin specimens retrieved from selected areas of paraffin-embedded tissues (PEC). The average time interval between cytological and histological diagnosis was 6 weeks. CIN I11 nuclei in CS and PEC specimen were Thionin-Feulgen stained and digitized. Beside the visual classification of DNA ploidy patterns, the 2 . 5 ~ and 5c exceeding rates and the specimen mean and standard deviation values of 21 photometric features were also analyzed. It was shown that, although there was a significant correlation between DNA ploidy patterns in corresponding PEC and CS specimen, the DNA patterns were dissimilar in eight of 22 cases. The DNA index, as represented by 2 . 5 ~ and 5c exceeding rates, was significantly higher in the CS specimen. High-resolution cytophotometric analysis of cell nuclei in CS and PEC specimens showed significant differences for a large number of nuclear photometric features. These findings can possibly be explained by differences in selection of CIN I11 cells from CS and PEC specimens and by differences between fixation procedures as used for the two techniques. It was concluded that cytophotometric data of CS and PEC specimens representing CIN I11 lesions should not be regarded as interchangeable. Key terms: DNA ploidy analysis, paraffin-embedded tissue, DNA image cytometry, CIN I11 'This study was supported by Praeventiefonds grants 28.1002. * n * * * k * * * * * m -rr* 2 --. 4 --.