Wilson disease is an autosomal recessive disorder of copper excess. This illness results from mutations of the ATP7B gene (chromosome 13, MIM# 277900). The discovery of the gene allowed a better understanding of cytosolic copper trafficking and its relationship with ceruloplasmin synthesis. Symptomatic patients may present with hepatic, neurologic or psychiatric forms. Clinical and phenotypic evidences provide only presumptive arguments for this disease which can be routinely assessed by molecular analysis. This genetic disease which can be efficiently treated was formerly biologically suspected after a careful but sometimes invasive study of copper metabolism. Genetic advances can now give a definite answer using linkage analysis and research for disease-causing mutations. However, this diagnosis strategy is limited since currently over 320 mutations and 80 polymorphisms have been currently identified.