Seventy French high-risk families were screened for germ-line BRCA-1 mutations. The BRCA-1 coding region and the exon-intron boundaries were sequenced, except when pre-screening by PTT revealed a truncated protein in exon 11. Germ-line BRCA-1 mutations were detected in 24% of families. The number of breast and ovarian cancers per family, a relative young age at ovarian cancer diagnosis, and the occurrence of breast and ovarian cancer in the same patient significantly predicted the presence of a BRCA-1 mutation. The low BRCA-1 mutation frequency suggested that some alterations were not detected and some families were probably BRCA-2 or BRCAx carriers.