Twenty cases of superficial endometriosis of the uterine cervix that occurred in patients from 20 to 51 (mean 37.1) years of age are described. The majority of the cases were seen in consultation and were usually referred because of diagnostic problems; endocervical glandular dysplasia, adenocarcinoma in situ, or rarely invasive adenocarcinoma were a frequent consideration of the contributor. The endometriosis was almost always an incidental microscopic finding. The endometriotic foci were usually confined to the superficial third of the cervical wall, but in one case there was also involvement of the middle third of the cervical wall. Deep cervical endometriosis was not present in any case. The endometriotic glands were typically evenly spaced and were surrounded at least focally by endometriotic stroma in all cases. The endometriotic stromal cells, however, were significantly obscured by inflammatory cells (two cases), inflammatory cells and hemorrhage (two cases), hemorrhage (four cases), and in one case by smooth muscle metaplasia causing initial failure to recognize the stromal component of the process. The presence of mitotic figures in the glandular epithelium contributed to an initial diagnosis of a premalignant or malignant glandular lesion being made or seriously entertained in 10 cases. Awareness that mitotic figures may be conspicuous in endometriosis from women of reproductive age, the usually bland cytologic features of the endometriotic epithelium, and the presence of associated endometrial stromal cells all facilitate establishing the correct diagnosis.