Haematuria can be macroscopic or microscopic in nature. Macroscopic haematuria is grossly visible in the urine, while microscopic haematuria is not apparent with the naked eye and is variably defined. There are numerous causes of haematuria, including pathology of the urinary and genital tracts, as well as more generalised bleeding disorders. Although haematuria can be asymptomatic, specific clinical signs may provide clues about the underlying problem. Diagnostic evaluation may require laboratory analysis, imaging, cystoscopy or open surgery, and management will ultimately involve treating the root cause. This article outlines the main diseases associated with haematuria, and describes the diagnostic work-up in dogs and cats.