Background: Expression of Phosphatase and Tensin homolog (PTEN) is lower in endometrial cancer in comparison with nor mal or hyperplastic endometrium. Loss of PTEN function by mutational or other mechanisms is an early event in endometrial tumorigenesis. Objective: In this study, we evaluated PTEN gene expression in hyperplastic and malignant endometrium to assess its diag nostic implications. Methods: This study was conducted on women presenting with abnormal uterine bleeding (AUB), attending the Outpatient and Inpatient Clinics of Obstetrics and Gynecology. Endometrial biopsy sections were routinely stained with HandE stain and im munohistochemical staining for PTEN expression was performed in all the endometrial lesions. Results: The study comprised 278 cases of endometrial hyperplasias and carcinomas. In simple hyperplasia without atypia (n=143), 80.0% showed intense PTEN positivity and 20.0% showed moderate PTEN positivity. Simple hyperplasia with atypia (n=15), 93.3% cases showed moderate PTEN positivity and 6.7% case showed intense PTEN positivity. Complex hyperplasia without atypia (n=76), 14.4% cases showed mild PTEN positivity and moderate PTEN positivity was seen in 85.6% cases. Com plex hyperplasia with atypia (n=34), 85.3% cases showed mild PTEN positivity and absent staining in14.7% cases. Adenocarci noma cases showed mild PTEN positivity in 10.0% and absent staining in 90.0% cases. Conclusions: PTEN expression decreases as the lesion progress from benign to frank malignancy, and loss of PTEN function is an early event in the pathogenesis of endometrial carcinogenesis.