The germline mutations of breast cancer susceptibility genes 1 (BRCA1) and breast cancer susceptibility genes 1 (BRCA2) have been associated with a significant increase in breast cancer risk and certain other cancers. Among the most known mutations in these tumor suppressor genes are 5382insC and 185delAG in BRCA1 and 6174delT in BRCA2. The aim of the current study was to investigate the frequency of these BRCA1 and BRCA2 mutations in southern Iranian familial and sporadic cases with breast cancer.Two hundred fifty women with sporadic breast cancer, 55 women with a familial history of breast cancer in their first degree-relatives and 200 healthy women formed the studied groups. DNA from peripheral blood mononuclear cells was extracted and analyzed by a multiplex polymerase chain reaction method. The data of this investigation indicated that the aforementioned founder mutations were not detected in the groups studied. Our results indicate that 5382insC and 185delAG mutations in BRCA1 and 6174delT in BRCA2 have much less frequency in Iranian breast cancer patients.