A retrospective study of 36,853 Papanicolaou smears recorded in our laboratory during the latter half of 1988 was undertaken to assess the effect of the absence or presence of columnar endocervical cells on the detection rate of cervical condyloma acuminatum and squamous dysplasia. We found that condyloma was diagnosed only slightly more frequently in smears with endocervical cells than in those without. However, cervical intraepithelial neoplasia was detected 2.3 times more frequently in smears with endocervical cells. The disparity in detection rate increased with higher grades of dysplasia. A significant difference in detection rate was maintained in all age groups except teenagers and patients 60 yr old and above. This suggests that smears lacking endocervical cells are less sensitive in screening for dysplasia and should be repeated when clinically appropriate.