Background: based on numerous epidemiologic and experimental studies it has been speculated that unopposed estrogen has a central role in development of endometrial benign, premalignant and malignant lesions. Endometrial cancer is the most common malignancy of the female genital tract, and the fourth most common cancer in women in developed countries. EC is the seventh most common cancer in women worldwide. Objective: To examine the effect of metformin on disordered proliferative endometrium and simple endometrial hyperplasia in comparison with progesterone to assess metformin clinical usefulness in these situations. Patients and Methods: All patients who referred for abnormal uterine bleeding (perimenopausal) and underwent endometrial office biopsy or D&C in our hospital and their tissue diagnosis was disordered proliferative endometrium (DPE) or simple hyperplasia (SH) were included in this study. Past medical history gathered from patients' interview records and patients with history of metformin sensitivity, renal failure, anorexia, anemia, skin rashes, diabetes mellitus, gynecologic neoplastic disorders and patients on estrogen or progesterone were excluded. Patients who fitted with including criteria were categorized in two groups in randomized fashion. Results: Our findings in this study revealed that metformin could be effective as well as progesterone in resolving of benign enodometrial proliferative lesions. Conclusion: The current study showed that treatment of the patients with abnormal endometrial proliferation (DPE and SH) with metformin induced endometrial atrophy and prevents abnormal cell growth and prevents perimenopausal bleeding subsequently.