Necropsy reports from 4,723 dogs examined from January 1990 to July 2010 in the Laboratório de Patologia Veterinária, Universidade Federal de Santa Maria, were surveyed. The main purposes of this retrospective study were to establish the prevalence and types of neoplasms of the urinary system in dogs. Neoplasms of the urinary system were present in 113 (2.4%) dogs. Twenty seven were primary neoplasms and 86 were metastatic or part of a multicentric tumor. The majority of the primary neoplasms were of epithelial origin. Thirteen dogs had primary renal neoplasms (prevalence of 0.27% over all dogs necropsied in the studied period). Cystadenocarcinoma/cystadenoma and renal cell carcinoma were the most prevalent primary renal neoplasms and transitional cell carcinoma was the most prevalent urinary bladder neoplasm. Metastatic (64 cases) or multicentric (22 cases) tumors affecting the urinary system were the most prevalent (86 cases [76.1%]). Among them, mesenchymal tumors were more common than epithelial tumors. Out of the 86 cases, most of them were localized in the kidney. Metastases of mammary tumors and multicentric lymphoma were the most prevalent histologic types.INDEX TERMS: Urinary system, diseases of dogs, epithelial and mesenchymal neoplasms, pathology.