Abstract: Objective BRCA1 has been known as breast cancer susceptibility genes which is closely associated with familial breast cancer and early onset breast cancer.The objective of our research is to investigate the prevalence of BRCA1 gene mutations among HeiLongJiang patients with familial or at early onset breast cancer.Methods 92 breast cancer patients with familial history or have suffered from breast cancer at the age of less than 35 years old were analyzed.A comprehensive mutation analysis(except exon1 and exon4)was performed through SSCP and subsequent DNA direct sequencing.Results In 92 breast cancers,five mutations were identified that included 3 novel mutations and 2 previously reported mutations which are all nonsense mutation.Conclusion The BRCA1 may play a very important role in familial breast cancer of HeiLongJiang population.Three novel mutations in BRCA1 may be mutations characterized to familial breast cancer of Chinese HeiLongJiang population.The mutation frequency of BRCA1 in familial breast cancer patients from HeiLongJiang is obviously lower than that in the western countries.However,the nonsense mutation 3712insG were detected in three patients which indicated that this mutation may be a founder mutation.