Koilocytotic atypia was found in 217 of 858 cervical biopsies obtained during a 26-mo. period. Koilocytotic change was more common in younger women. Nuclear atypia in the koilocytotic cells was associated with cervical dysplasia in a high proportion of cases. There was a significant difference in the incidence of dysplasia in koilocytosis with marked nuclear atypia when compared to koilocytosis without nuclear atypia. In some cases koilocytosis was associated with vesicular changes in the cervical epithelium. The significance of this change and its association with other abnormalities of the cervix is discussed.