Mutation in BRCA1 and BRCA2 genes increases the risk of breast and ovarian cancer. Identifying the mutation is a key to prevent and treat the mutation-caused cancer. China has the largest population of 1.4 billion in the world. By testing BRCA1/2 genes in 11,386 non-cancer Chinese Han individuals, we determined there is one BRCA mutation carrier in every 265 Han Chinese individuals in the tested individuals, and we estimated there are 5.1-million BRCA mutation carriers in the 1.3-billion Chinese Han population. Our study provides a fundamental information to prevent and treat the BRCA mutation-caused cancer in the Chinese Han population. (By Dr. San Ming Wang, https://jmg.bmj.com/content/early/2020/05/28/jmedgenet-2020-106970 )