A group of 103 sicilian patients with hereditary and familiar breast and/or ovarian cancer were screened for Breast Cancer 1 gene (BRCA1) mutations by direct sequencing PCR products spanning the coding region and partial intronic regions of the BRCA1 gene. In this study, we report a new germline mutation in BRCA1 gene, not previously reported in the BIC database, in a woman with ovarian cancer at 46 years old. Mother's proband has been diagnosed the same histotype of ovarian cancer at 42 age. The mutational analyses that shown a 4843delC frameshift mutation in exon 16 of BRCA1 gene was extended to other family members including the proband's brother and her two sons. Direct automatic sequencing of DNA extracted from the lymphocytes showed exactly the same 4843delC frameshift mutation only in the brother. In conclusion, the characterization of this mutation could help in the identification of a founder mutation of sicilian area and this may provide significant advantages for genetic counselling.