The purpose of this study is to describe the cellular characteristics of endometrial hyperplasia without/with atypia in cervical smears. These cellular features were compared with those of normal endometrium and endometrial carcinoma. We reviewed 265 cervical smears : 64 normal proliferative endometrium, 118 endometrial hyperplasia without atypia, 21 endometrial hyperplasia with atypia, and 62 endometrial adenocarcinoma. Of these smears, 72(27.2%) smears which had diagnostic endometrial epithelial cells were selected for this study. The cytologic abnormalities about cellularity, background, changes in cellular architecture, alterations in nuclear size, anisokaryosis, chromatin pattern, nucleoli, cytoplasmic vacuoles, and mitosis were observed. Nuclear enlargement(1.6 to 2 times of the nucleus in the intermediate squamous cell) and anisokaryosis(${geq}$2 fold in size variation) were highly suggestive of endometrial hyperplasia without/with atypia. The nuclei from endometrial hyperplasia with atypia were more coarsely granular in chromatin patterns than hyperplasia without atypia(33.3% vs 3.4%). Micronucleoli were observed in all endometrial conditions, but the presence of macronucleoli were more suggestive of hyperplasia with atypia(22.2%) and adenocarcinoma(55%). The changes in cellular architecture(loss of polarity, uneven internuclear distance, overlapping and loose arrangement) were seen in hyperplasia with atypia and adenocarcinoma. Characteristically, bloody background was seen in endometrial hyperpiasia, and cellular detritus or granular proteinaceous material was only observed in endometrial adenocarcinoma. Mitoses were also observed in adenocarcinoma. In conclusion, although there is no single parameter useful for the cytologic differential diagnosis of endometrial lesions, combined cytologic evaluation can be used to diagnose hyperplasia cytologically.