We studied DNA polymorphisms for five new chromosome 13 markers in 52 Wilson's disease (WD) families from Europe, North America, and the Middle East. There was significant evidence for linkage between the Wilson's disease locus (WND) and all the marker loci. Multilocus linkage analysis, using a genetic linkage map established from reference pedigrees, suggested that WND is most likely between D13S31 and D13S59, at distances of 0.4 and 1.2 centimorgans, respectively. Our results suggest that the chromosomal location of the Wilson's disease gene is the same in all families from the populations studied. This evidence and the availability of many close, flanking, and polymorphic DNA markers make possible accurate and informative testing of potential carriers and WD homozygotes in families with at least one previously affected child. An advantage of a genetic linkage test over other laboratory methods for prediction of genotype in WD is that a reliable diagnosis can be made at a much earlier stage in life, including prenatally. In addition, DNA testing can be used in place of an invasive liver biopsy procedure to confirm a diagnosis in patients with borderline serum ceruloplasmin levels. Presymptomatic identification will also allow therapeutic intervention to prevent symptoms before irreparable liver or neurologic damage occurs. We describe the implementation of prenatal and preclinical diagnosis for two families with WD.