Breast cancer is a leading cancer in American women. About 7% of breast cancer is due to inheritance of mutated genes BRCA1 and BRCA2. Numerous investigations have revealed a number of mutations in BRCA1 and BRCA2 genes. The inheritance of the mutated BRCA1 or BRCA2 genes accounts for 45% and 35%, respectively, of hereditary breast cancers. A central database named Breast Cancer Information Core (BIC) has been established in the National Human Genome Research Institute (NHGRI) to coordinate the information related with BRCA1 and BRCA2 research. Nearly half of the mutations (49%) in the BRCA1 gene are frameshift mutations and the cancer-causing mutations account for 66% of all entries. However, for the BRCA2 gene frameshift mutations and cancer-causing mutations account for only 35% and 43%, respectively, of all entries. The significance of a large portion of missense sequence variants (24% of BRCA1 mutations and 47% of BRCA2 mutations) needs further evaluation. The incidence of 185delAG and 5382insC in BRCA1 gene and 6174delT in BRCA2 gene is predominantly high and the founder effect of these mutations is discussed.