The endometrium is a unique hormonally regulated organ, capable of cyclically responding to steroid ovarian hormones, resulting in a spectrum of distinct morphological changes. Exogenous hormonal therapy is indicated in a myriad of clinical conditions. The effects of exogenous hormone on the endometrium depend on the types, dosage, and the duration of its exposure. These morphological changes range from benign (atrophic or inactive endometrium, polyps, secretory changes) to precancerous (endometrial hyperplasia with or without atypia) to cancerous conditions (endometrial carcinoma). A significant proportion of endometrial specimens are sent to the surgical pathological laboratories to evaluate therapy effects and treatment efficacy. It is of utmost important for the attending surgical pathologist to be familiar with the possible histological patterns in the endometrium that are associated with each hormonal therapy in order to render an accurate and practical diagnosis. This chapter provides detailed histomorphological descriptions of the changes encountered in the endometrium following some of the most widely used hormone therapies: oral contraceptives, hormone replacement therapy, ovulation induction, gender-affirming therapy, and antineoplastic hormone therapy.