A superficial koilocytotic lesion progressing to dysplasia and later into an aggressive invasive cervical cancer has been demonstrated. It is thought that these lesions create an area of susceptibility to neoplasia in the cervix, vagina, and in the vulva, and are defined as preneoplastic lesions. A total of 57 young women have been examined cytologically and colposcopically at least 3, 6, and 12 months following CO2-laser surgery. In 12 women (21%) the lesions were multifocal with the same histological pattern in the cervix and in the vagina and/or in the vulva. CO2-laser effectively eradicates the koilocytotic lesions in the cervix and in the vagina; in the vulva, however, relapses are common after an initial good effect. The diagnostic accuracy of cervicovaginal cytology was low: exfoliated koilocytotic cells were found in only 26.3% out of 57 cases with histologically proven koilocytotic lesion, even when the cytological smears were reexamined.