This prospective study was designed to determine the urinary concentrations of purine metabolites in healthy and diseased dogs. The goals were to test the hypothesis that urine concentrations of terminal purine metabolites will identify dogs with diseases that disturb purine degradation. Five hundred and sixty-three client-owned dogs admitted sequentially to the veterinary medical centre were included. Dogs were divided into groups on the basis of their disease. Urine concentrations of xanthine, uric acid, allantoin and creatinine were measured by high-pressure liquid chromatography. Xanthine and uric acid to creatinine ratios were significantly increased in dogs with chronic kidney disease (p = 0.01). The uric acid to creatinine ratio was significantly increased in dogs with cancer compared with clinically healthy dogs (p = 0.04), and significantly increased in dogs receiving chemotherapy for their disease (p < 0.01). Compared to clinically healthy dogs, xanthine and uric acid to creatinine ratios were significantly increased in dogs with hyperadrenocorticism (p < 0.01, and 0.04, respectively). Therefore, the results of this study found that the urinary concentrations of purine metabolites in dogs are significantly impacted by systemic disease. Cancer, chronic kidney disease, and hyperadrenocorticism are associated with altered concentrations of urinary purine metabolites in dogs.