Haematuria (blood in the urine) is commonly seen in feline practice and can vary from very mild and only detectable on dipsticks (most common) to severe gross haematuria. It may be caused by blood leaking into any part of the urinary tract (kidneys, ureters, bladder, urethra) or the associated reproductive tract (e.g. prostate, prepuce, uterus, vagina), or it can result from a haemostatic defect, where the degree of haematuria may be very severe and grossly evident. This chapter considers aetiology and differentials, diagnostic approach and management.