Wilson disease (WD) is an autosomal recessive disorder of copper transport. WD patients are presenting with a wide range of heterogeneous clinical syndromes including hepatic, neurological, or psychiatric presentations. The disease is caused by mutations in the ATP7B gene. This study presents the results of comprehensive mutation analysis in 227 WD patients from 200 unrelated families (173 from Czech Republic and 27 from Slovakia). More than 80% of all mutant alleles were identified, using a combination of PCR/RFLP, DGGE, TTGE, DHPLC, and sequencing. A total of 40 different mutations and 18 polymorphisms were detected on 400 independent mutant chromosomes. The most common molecular defect was H1069Q (57% of all 400 studied alleles). Each of the other 39 mutations was present in no more than 4% of WD alleles and 23 mutations were found in only one WD allele each (0.25%). Thirteen novel mutations were identified, including seven missense mutations (L641S, T737R, D918E, T1033S, G1111D, D1271N, and G1355C), four small deletions (19_20delCA, 1518_1522del5, 3140delA, and 3794_3803del10), and two splice-site mutations (2446-2A>G, 2865+1G>A). We did not find a significant correlation between H1069Q homozygosity and age of onset, and clinical and biochemical manifestation. Our data provide evidence that the H1069Q mutation-the most common molecular defect of the ATP7B gene in the Caucasian population-originates from Central/Eastern Europe. Screening of five prevalent mutations is predicted to reveal 70% of all mutant alleles presented in WD patients. This will provide a good starting point for early clinical classification of WD in our population.