Objective: The aim of this study was to investigate malignancy potential in endometrial hyperplasias and association with PCNA and Ki-67. Methods: Hysterectomy or probe curettage materials of 62 patients (20 simple hyperplasias (SH), six SH with atypical changes, five complex hyperplasias (CH), 11 CH with atypical changes, ten proliferative endometrium (PE) and ten secretory endometrium) were included in our study. Immunohistochemical staining for PCNA and Ki-67 protein was performed on formalinfixed and paraffin-embedded tissue samples. Results: Immunoreactivity of PCNA was found to be significantly higher in atypical CH as compared to all other groups (p < 0.05). Also immunoreactivity of PCNA was significantly lower in SH as compared to atypical CH, and PE (p < 0.05). Average values showed that Ki-67 immunoreactivity is highest for atypical CH, and PE. Immunoreactivity of Ki-67 was found to be significantly higher in atypical CH as compared to other groups except PE (p < 0.05). Conclusion: PCNA immunoreactivity can be useful in patients with endometrial CH showing mild or moderate atypical changes in terms of prefering more conservative treatment modalities in those with low PCNA index. Also we suggest that Ki-67 could be insufficient to determine the potential of malignancy.