The objective of this study was to review a 5-year experience with atypical glandular cells of undetermined significance (AGUS) on Papanicolaou smear and to use the information to devise a triage method for patients presenting with this abnormality. Our Papanicolaou smear database was used to identify patients who were found to have AGUS results between January 1, 1994 and December 31, 1998. The medical records of these patients were reviewed for the results of follow-up studies, including repeat Papanicolaou smear, endocervical curettage, colposcopic directed biopsies, and endometrial biopsy. During the study period, 27,859 Papanicolaou smears were performed, with 306 (1.1%) being reported as AGUS; 18 patients had two AGUS smears. An additional 24 patients did not meet study criteria. The study group then consisted of 264 patients, of whom 244 (92.4%) reported for follow-up. There were 167 (63.3%) with atypical endocervical cells of undetermined significance (AECUS), 14 (5.3%) with atypical endometrial cells of undetermined significance, and 83 (31.4%) with AECUS plus a squamous cell abnormality. The overall prevalence of a high-grade squamous intraepithelial lesion (HSIL) was 11.8%. The prevalence of HSIL in the AECUS plus squamous cell abnormality group was 25.4%. None of the atypical endometrial cell group had HSIL. In the AECUS, favor dysplasia category, 29.4% had HSIL, whereas in the AECUS, favor reactive process or in unqualified, 2.3% had HSIL. Eighty-one patients underwent endometrial biopsy: three (3.7%) were found to have endometrial adenocarcinoma, and two (2.5%) had complex atypical endometrial hyperplasia. The prevalence of HSIL in patients with AECUS, favor reactive process or AECUS, unqualified Papanicolaou smears is low. Colposcopy is not necessary as an initial triage process for this category of patients. A significant percentage of patients with AECUS, favor dysplasia or AECUS with a squamous epithelial abnormality Papanicolaou smears have HSIL; this subset of patients should be investigated with colposcopy.