The detection of endocervical glandular abnormalities has risen in recent years due to the increased clinical use of improved endocervical canal sampling instruments, such as Cytobrushes. From January 1987 through August 1989, a diagnosis of endocervical glandular dysplasia was initially suggested on cervical smears from 50 women for whom histologic follow-up information was available. Retrospective review of the cytologic smears and histologic slides from these patients revealed tubal metaplasia in 19 of 29 (66%) cases evaluated by cervical conization and/or hysterectomy and in 19 of 21 (90%) cases confirmed by cervical biopsy and/or endocervical curettage. Cytologic criteria for the diagnosis of tubal metaplasia on cervical smears are discussed. Inasmuch as adenocarcinoma in situ of the cervix and endocervical glandular dysplasia are not readily discernible by colposcopy, the responsibility for the diagnosis of these lesions lies with surgical pathologists and cytopathologists. Familiarity with the cytologic features of adenocarcinoma in situ and endocervical glandular dysplasia that distinguish these lesions from tubal metaplasia and other potential mimics is essential.