This chapter explores the management of contralateral breast cancer in patients with BRCA1 and BRCA2 mutations, focusing on two primary strategies: contralateral risk-reducing mastectomy (CRRM) and intensified surveillance using imaging techniques such as contrast-enhanced breast MRI. BRCA mutation carriers face a significant risk of developing contralateral breast cancer. CRRM significantly reduces the risk of contralateral breast cancer, but the procedure carries surgical risks and potential impacts on quality of life. Surveillance aims to detect cancer early through regular imaging, balancing the psychological burden of ongoing cancer risk with the avoidance of surgical intervention. This document explores the benefits, risks, and implications of each strategy and highlights the importance of making evidence-based, individualized decision-making. The analysis is based on the Japanese Organization of Hereditary Breast and Ovarian Cancer (JOHBOC) guidelines from Japan and recent research findings, aiming to provide comprehensive recommendations for high-risk women.