Abstract Women who inherit a pathogenic variant (mutation hereafter) in the BRCA1 or BRCA2 geneface extremely high lifetime risks of developing breast and ovarian (or fallopian tube) cancer. More than two decades since the discovery of these genes, and primary prevention with bilateral mastectomy and salpingo-oophorectomy remain the most effective options to manage cancer risk in this population. Understanding the impact of exogenous hormone use is important for both the clinical management of high-risk women and for furthering our knowledge of the pathogenesis of BRCA-associated disease. In this session, I will review the current epidemiologic data surrounding the role of exogenous (anti)hormone use on BRCA-cancer risk. Specifically, I will discuss the role of tamoxifen in preventing BRCA-associated breast cancer and I will describe whether use of oral contraceptives or hormone replacement therapy (HRT) increase the risk of breast cancer. Where possible, I will present data by gene mutation. Potential associations with the risk of ovarian cancer will also be referred to, given that managing BRCA-cancer risks is a balancing act. Finally, I will review how the epidemiologic information has contributed to the discovery of novel targets for the non-surgical prevention of BRCA1-associated breast cancer and gaps in the literature to be addressed in future research. Citation Format: Joanne Kotsopoulos. Hormonal exposure and risk in BRCA1/2 carriers [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr ED2-3.