To ascertain the significance of squamous atypia encountered during routine Papanicolaou smear screening in pregnancy, we reviewed our experience with 76 pregnant women seen during a 4-year period. All were evaluated with repeat cytology and colposcopy during pregnancy and again postpartum. Colposcopic examination during pregnancy revealed a normal transformation zone without evidence of intraepithelial neoplasia in 46 women. In six of these women, repeat cytology was interpreted as cervical intraepithelial neoplasia (CIN) grade 1. In 30 women, an abnormal transformation zone was identified--14 with a negative repeat cytology. In five women, the transformation zone was interpreted as compatible with CIN 2 or CIN 3. Colposcopically directed biopsies were performed in 31 women, in all but two postpartum. Of the 76 women, human papilloma virus or CIN was identified on biopsy in 16 women (21%). We propose that an isolated report of atypical squamous cells on cervical cytology obtained at the initial prenatal visit does not warrant colposcopic evaluation during pregnancy, unless a repeat cytology suggests CIN. Repeat cytology and evaluation to exclude infections and inflammatory lesions is appropriate. However, if a subsequent cytology is abnormal, postpartum colposcopy and colposcopically directed biopsies seem appropriate, since the prevalence of HPV or CIN was 21%.