Breast cancer in Tunisia is characterized by a much higher incidence of aggressiveness compared with Western countries. The pattern of allelic loss at the BRCA1 locus in Tunisian women with breast carcinoma has not been studied. Therefore, the aim of this present preliminary study was mainly focused on loss of heterozygosity (LOH) analysis of the BRCA1 gene to determine if this tumor suppressor gene is involved in sporadic breast carcinoma among Tunisian women. We investigate allelic losses by analyzing three microsatellite markers in the BRCA1 region, in a panel of 21 human breast tumors. D17S1322 marker had the highest frequency of LOH (59%), followed by the D17S1323 (35%), and EDH-17B (20%). Collectively out of 21 informative cases 13 (62%) showed LOH at at least one BRCA1 locus. This data provides evidence that allelic loss at BRCA1 is a frequent event in sporadic breast tumorigenesis among Tunisian women, and suggests that the BRCA1 gene might play an important role as a tumor suppressor gene.