This article is to determine the clinical significance and underlying pathology among patients with atypical glandular cells (AGC) identified during cervical Papanicolau (Pap) smear screening. AGC slides were searched from 51,412 computerized files of the cytology laboratory of Mackay Memorial Hospital during a 29-month period. The results of clinical evaluations were reviewed and an experienced gynecologic cytopathologist who was not involved in the original cytologic diagnosis and was not aware of the clinical results of the follow-up examinations rechecked all AGC slides. We used the z score to determine whether different results were achieved after the gynecologic cytopathologist rechecked the slides. We further analyzed all slides with different cytologic diagnoses and compared results with the histologic diagnoses. Forty-nine cases were initially identified as AGC. Among these, 29 were reviewed and identified as AGC again, and the result of biopsies revealed that they were all chronic cervicitis, ie, negative for malignancy or premalignancy. The other 20 cases were reviewed and diagnosed as non-AGC. Among the results of cytologic examinations, seven had inflammation, two had atypical squamous cells of undetermined significance (ASC-US), ten had high-grade cervical intraepithelial neoplasia (CIN), and one had adenocarcinoma. The results of histologic diagnosis included eight cases with normal tissue, two with CIN grade 1, eight with high-grade CIN, one with microinvasive squamous cell carcinoma, and one with adenocarcinoma. Histologic results revealed 20.4%1 (10/49) and 50% 1(10/20) at initial cytologic diagnosis of AGC and expert-reviewed non-AGC, respectively, which were finally at least high-grade CIN. According to the gynecologic cytopathologist's diagnosis, 59.2%1 (29/49) of cases would have eliminated unnecessary histologically diagnostic procedures. In conclusion, clinicians should be careful about the significance of the cytologic diagnosis of AGC, because there may actually be an underlying pathology, which can be identified by a pathologist who is an expert in gynecologic cytopathology. The interobserver variation in diagnosing AGC favors specialized training in gynecologic cytopathology. In addition, prompt diagnostic interventions, including colposcopy, endocervical curettage, and/or endometrial biopsy, should be performed after confirmation of the diagnosis of non-AGC by an experienced gynecologic cytopathologist.