In this study, a Lebanese woman with severe factor XI deficiency as well as several unaffected family members were analysed. The F11 gene was screened by polymerase chain reaction amplification of all 15 exons, including intron-exon junctions followed by single-strand conformational analysis. Variant single-strand conformational analysis profiles were obtained for exon 13; sequencing of these products allowed the identification of a novel missense mutation (Trp501Cys) situated in the catalytic domain, in homozygosity in the proband.