Objectives: The aim of present study was to determine expression of cyclin E in endometrial hyperplasia without atypia, atypical endometrial hyperplasia and endometrial cancers in comparison with expression of cyclin E in atrophic endometrium of postmenopausal women. We have also estimated relationship between cyclin E expression and prognostic factors for endometrial cancer such as: histological type, cancer stage and histological grade. Material and methods: 154 women were enrolled into study. Women were divided into 4 groups. The first group consist of 38 women with endometrial hyperplasia without atypia, the second group consist of 18 women with atypical endometrial hyperplasia. The third group comprise 62 women with endometrial cancer and the forth 36 women with atrophic endometrium. Cyclin E expression was estimated in formalin-fixed, paraffin-embedded tissues obtained from enrolled women with the use of immunohistochemical techniques. We estimated labelling index (LI) – the number of cells that stained for cyclin E in relation to all cells at the certain field of view. Results: Medians of labelling indices of cyclin E in atrophic endometrium, endometrial hyperplasia with atypia, atypical endometrial hyperplasia end endometrial cancer were 13,7%, 34,7%, 62%, 72,2% respectively. These differences were statistically significant. In our study we haven’t found relationship between cyclin E expression and histological type of tumour (p=0,186), cancer stage (p=0,186) and histological grade (p=0,539). Conclusions: In the carcinogenesis of endometrial tumours in postmenopausal women there is a progressive disorder in mechanisms regulating cell cycle. It seems impossible to use cyclin E as prognostic factor for endometrial cancer.