OBJECTIVES: Untreated hormonal disturbances connected with unbalanced estrogen serum concentrations can influence on pathological proliferation of endometrium. The aim of the study is to assess the effect of GnRH agonists on endometrium in women consulted due to simple hyperplasia endometrium. MATERIAL AND METHODS: 15 women in the mean age 48.5 +/- 3.5 years with the histopathological diagnosis of simple hyperplasia were treated with trioptorelin during 3 months. After therapy all patients were undergone transvaginal ultrasonography and endometrial biopsy. RESULTS: Atrophic endometrium were observed in all women after a 3-month therapy. The thickness of endometrium decreased from 10.21 +/- 3.2 mm to 3.94 +/- 1.56 mm. CONCLUSIONS: The efficacy of the therapy of simple hyperplasia in women with GnRH agonist was 100%.