Wilson disease (WD) is an autosomal recessive disorder caused by mutations in the ATP7B gene, yet many patients have either one mutation, or no mutation. We investigated whether the mutation detection rate is associated with any biochemical characteristics of WD. In a study of 71 patients, we used PCR-sequencing to screen for ATP7B mutations in 7 exons (exons 8, 10, 11, 14, 15, 16, and 18) covering 95% of known mutations in Korean patients with WD. We also investigated serum concentrations of various biochemical analytes. Data were analyzed by linear association test and one-way ANOVA. Based on the number of detected ATP7B mutations, a significant difference in serum ceruloplasmin concentration was found among the 3 groups (p <0.001). Serum ceruloplasmin concentration averaged 3.32 +/- 1.74, 10.8 +/- 5.50, and 14.9 +/- 3.88 mg/dl (mean +/- SD) in the 25, 20, and 26 patients with two, one, and no ATP7B mutations, respectively. We observed 82.9% and 16.7% of mutant allele frequency in WD patients with ceruloplasmin concentration <10 mg/dl and 10-20 mg/dl, respectively (p <0.001). Thus serum ceruloplasmin concentrations among WD patients differed according to the number of ATP7B mutations detected.