BACKGROUND Wilson's disease diagnosis is still a challenge for clinicians. AIM To underline the importance of genetic testing in carrier detection and diagnosis of atypical Wilson's disease cases. METHODS Two families with Wilson's disease in two consecutive generations were analysed with clinical, biochemical and genetic testing. RESULTS In one family with triplet siblings, two of whom monozygotic, molecular screening of ATP7B, the gene responsible for Wilson's disease phenotype, allowed detection of 3 disease alleles, the discrimination between carrier and disease state and the postmortem diagnosis of Wilson's disease in the siblings' father. In the second family, molecular analysis detected 3 disease alleles and confirmed the diagnosis of Wilson's disease in two asymptomatic monozygotic twins. CONCLUSION These results demonstrate that mutational analysis is determinant for carrier identification and diagnosis of atypical Wilson's disease patients.