Classification of endometrial cells on cervical cytology. One hundred eighty-eight women who had endometrial cells on cervical cytologic specimens during the secretory phase or in the postmenopausal period were studied retrospectively. Each had undergone hysterectomy or endometrial biopsy within 12 months of the original smear. The endometrial cells were classified as typical, atypical, or suspicious for carcinoma. Among premenopausal subjects, three of 57 with typical cells had endometrial hyperplasia, one of two with atypical cells had endometrial polyps, and both with cells suspicious for carcinoma had endometrial carcinoma. In the postmenopausal group, ten (13.5%) of 74 with typical endometrial cells had either hyperplasia or carcinoma, and five (22.7%) of 22 with atypical cells and 24 77.4%) of 31 patients with suspicious cells had either hyperplasia or carcinoma. The present findings and a review of the pertinent literature demonstrate that the classification system used is helpful in predicting the risk for endometrial disease in patients with endometrial cells seen on cervical cytologic smears during the secretory phase or in the postmenopausal period. 