The recently proposed Bethesda system for cervical/vaginal cytology has made a standardization related to "atypia". In cellular changes due to inflammation or repair, the word "benign cellular change" has been suggested as a substitute for atypia. Terminology related to atypical cells may become standardized, but the cytologic criteria has not been well defined yet. We evaluated 160 cases of atypical squamous cells of undetermined significance(ASCUS) by the Bethesda Sys4em(TBS). Among 30,428 cases screened, a cytologic diagnosis of ASCUS was made in 498 cases(1.6%) and 160 cases were histologically verified ASCUS was diagnosed based on nuclear enlargement and nonclassical signs of condyloma. The results are as follows: One hundred and twenty three cases(76.9%) revealed chronic cervicitis. Thirty seven cases(23.1%) demonstrated squamous intraepithelial lesion. Among intraepithelial lesions, condyloma and mild dysplasia were 28 cases(75.7%). Moderate and severe dysplasia were 5 cases(13.5%) and 4 cases(10.8%), respectively. it is concluded that patients with ASCUS should be colposcopically examined.