Copper toxicosis (CT) is a common autosomal recessive disorder in dogs. Recently, the CT locus was closely linked to microsatellite marker C04107. Currently, the gene underlying CT is unknown. In contrast to that of many other animals, knowledge regarding the canine karyotype is quite sparse. Except for the X and Y, all the chromosomes are acrocentric. Peripheral blood was used in this study and high-resolution G-banding and FISH were performed on dog chromosomes. In order to evaluate the chromosomal locus of the ATP7B gene (Wilson F4 and Wilson B1), CTR1 and the C04107 marker were isolated from canine BAC clones. Dual-color FISH results showed that BAC clones containing Wilson F4, Wilson B1, C04107 marker and CTR1 were localized on chromosomes 4q23, 22q11, 10q26 and 11q22.2-22.5, respectively.