The cytologic diagnosis of endometrial cancer using material obtained with the Endocyte endometrial sampler was assessed for 874 patients. The samples obtained were smeared directly on slides for fixation and staining; the smears were more difficult to assess than cervicovaginal smears, however, due to the presence of blood, the small size and density of the cells and the flattened three-dimensional architecture of the tissue fragments obtained. Only 8.2% of the samples were classified as inadequate; repeat sampling in some of those cases produced diagnostic material. All 12 cases of carcinoma (including one case in a woman less than 40 years of age) were diagnosed by cytology as malignant; however, the original cytologic sample in one of those cases was inadequate. For the diagnosis of benign versus malignant, cytology had a sensitivity of 92%, a specificity of 100% and predictive value of 100%. Cytology also diagnosed as suspicious the smears from 5 of 13 cases of endometrial hyperplasia and 2 of the 9 cases of endometrial polyps. The cytologic findings for benign and malignant samples are described and illustrated in detail. Relative to other endometrial sampling devices, the Endocyte is inexpensive and was easily used by the gynecologist and well tolerated by the patients, with no complications and minimal discomfort.