OBJECTIVE: To determine the clinical implications of atypical glandular cells of uncertain significance (AGCUS) in cervical cytologic smears. STUDY DESIGN: Retrospective analysis. RESULTS: Eighty-eight of 32,281 (0.27%) cervical smears obtained during the study period contained AGCUS. Of the 47 women with AGCUS, 16 had intraepithelial or invasive neoplasms (34%; 95% confidence interval, 21-49%), including 9 low, or high grade squamous intraepithelial lesions, 1 adenocarcinoma in situ of the cervix, 3 adenocarcinomas of the cervix, 2 adenocarcinomas of the endometrium and I adenoid basal cell carcinoma of the cervix. CONCLUSION: The high prevalence of cervical and endometrial neoplasia among women with the isolated finding of AGCUS on cervical cytologic smears warrants a thorough diagnostic evaluation.