ABSTRACT: In dogs, diseases of the urinary tract are common and can be caused by disorders of varied etiology. The objective of this study was to classify qualitatively and quantitatively urinary tract lesions of 363 dogs, which were classified according to its anatomical distribution and etiology. The data was obtained from the revision of 36 years of protocols from the Regional Laboratory of Diagnosis (LRD/UFPel) and it represents 4.0% of diagnoses from a total of 8980 for that period and species. Renal injury accounted for 93.1% of cases, with 309 being primary kidney lesions; from which the main lesions were the tubulointerstitial nephritis (142 cases) often associated with Leptospirosis (47). Injuries of lower urinary tract accounted for 6.9% of the cases where acute cystitis stands out (19). In this study, renal failure, acute or chronic, represented an important cause of death in dogs.