Between 1984 and 1992, we reinvestigated 170 cases of cervical smears obtained in conization or hysterectomy which had produced false positive cytologic findings. We looked for morphological changes that could explain the cytologic findings. Such changes were found in half of the cases. These cases included 54 (63.6%) specimens with marked cellular polymorphism as a result of inflammation, tissue regeneration, or atrophy. In 51.9% of the cases showed histologic signs of possible HPV infection. The initial findings required reclassification in 12.9% of the cases, and in fifteen cases (17.6%) the biopsy matched the cytologic findings, without being validated by the final findings. We observed histologic phenomena corresponding to the cytologic findings in 30.8% of the cases in group IIID (n = 26) using Papanicolaou's classification system. In groups IV a (n = 72), IV b (n = 44), and V (n = 28), we found a histologic explanation in 54.2%, 47.7%, and 60.7% of the cases, respectively. In most cases we observed polymorphic cellular changes primarily associated with HPV.