Wilson disease (WD) results when specific mutations occur at the ATP7B gene. The presence of mutations in the ATP7B gene was studied in the coding region and the intron-exon boundaries in 15 WD Spanish patients, and their first-degree relatives when possible. A total of 20 nucleotide sequence changes were detected, 18 missense and two splicing mutations. Six of these variants were classified as disease-causing mutations, five missense, and one splicing; four of them have been previously described (M645R, A1065P, H1069Q, and 3060 + 5G > T), whereas two were novel (P768L and A990P). No mutation was clearly prevalent, although the H1069Q mutation predominated, nor did a good phenotype-genotype correlation exist. The two new mutations described were manifested as an asymptomatic increase in serum transaminases. The remaining 14 changes were classified as polymorphisms and their potential effects on protein function are discussed. The identification of mutations in the ATP7B gene has allowed a conclusive diagnosis to be made of WD in patients presenting neurological phenotype or neurological of hepatic phenotype, who would otherwise not have been diagnosed using classical criteria. WD patients could start chelating treatment earlier on and possibly modify the natural progression of the disease.