The cytologic criteria for the diagnosis of endocervical gland involvement (EGI) by high-grade squamous intraepithelial lesions (HGSILs) have been described, and this diagnosis occasionally is made. This study evaluates the accuracy of a cytologic diagnosis compared with that of follow-up cone biopsies. Twenty-eight patients with Papanicolaou (Pap) smear diagnoses of HGSILs with EGI, with follow-up cone biopsies, were identified from New York University computerized files. Results were compared with those of a control group of 28 patients showing cervical intra-epithelial neoplasia grades II/III (CIN-II/III), irrespective of previous Pap smear findings. On subsequent cone biopsy samples, 26 of the 28 study cases showed signs of HGSIL. Of these 26 patients, 17 (65%) showed evidence of HGSIL with EGI. Among the 28 control cases, 20 (71.4%) had EGI on the cone biopsies (P = NS). We also examined previous Pap smear findings in a control group of 42 cone biopsies with CIN-II or CIN-III, with or without EGI. EGI was diagnosed in previous Pap smears in 3 of the 31(10%) cases that showed signs of EGI on cone biopsies and in 2 of the 11 cases (18%) that did not evidence EGI on subsequent cone biopsies (P = NS). In our experience, the cytologic diagnosis of EGI on Pap smears did not identify a group of patients with increased frequency of EGI on subsequent cone biopsies.