Calculi were located in the kidneys, the ureters and the bladder of a two-year-old male dachshund. The yellow-greenish calculi developed as a result of impaired transformation of xanthine to uric acid resulting in an increased concentration of xanthine in the urine. The cause of the impaired catabolism of xanthine was probably a disorder of the xanthine oxidase enzyme, which catalyses the transformation of xanthine to uric acid.