Werner's syndrome (WS) is a rare autosomal recessive disorder, one of the progeroid syndromes, characterized by features of premature aging. The genetic defect in WS is unknown but recently the genetic linkage of WS to several markers on the short arm of chromosome 8 has been reported. Genetic analysis of 25 families with WS demonstrated that D8S339 was the closest marker linked to the gene locus for Werner's syndrome (WRN), with a peak lod score of 18.29 at recombination frequency 0.001, and showed a linkage disequilibrium with the WRN locus. We studied two unrelated families with WS using ANK1, D8S339, and D8S360. The mutative haplotype identified through the generations in pedigrees provides a means of carrier detection and presymptomatic diagnosis.