The prevalence of BRCA1 gene mutations in breast cancer differs between diverse ethnic groups. Relativelylittle information is known about patterns of BRCA1 mutations in early-onset breast cancer in women of Uighuror Han descent, the major ethnic populations of the Xinjiang region in China. The aim of this study was to identifyBRCA1 mutations in Uighur and Han patients with early-onset (age <35 years), and sporadic breast cancer forgenetic predisposition to breast cancer. For detection of BRCA1 mutations, we used a polymerase chain reactionsingle-stranded conformation polymorphism approach, followed by direct DNA sequencing in 22 Uighur and 13Han women with early-onset sporadic breast cancer, and 32 women with benign breast diseases. The prevalenceof BRCA1 mutations in this population was 22.9% (8/35) among early-onset sporadic breast cancer cases. Ofthese, 31.8% (7/22) of Uighur patients and 7.69% (1/13) of Han patients were found to have BRCA1 mutations.In 7 Uighur patients with BRCA1 mutations, there were 11 unique sequence alterations in the BRCA1 gene,including 4 clearly disease-associated mutations on exon 11 and 3 variants of uncertain clinical significance onexon 11, meanwhile 4 neutral variants on intron 20 or 2. None of the 11 BRCA1 mutations identified have beenpreviously reported in the Breast Cancer Information Core database. These findings reflect the prevalence ofBRCA1 mutations in Uighur women with early-onset and sporadic breast cancer, which will allow for provisionof appropriate genetic counseling and treatment for Uighur patients in the Xinjiang region.