The leading causes are disease, hormones, and environmental factors. Here, too, it is advisable to first have a urinary and physical examination by the veterinarian. Castration is often an effective solution to this problem (even unsterilized cats can start spraying during heat). Marking with urine can reduce stress factors. For example, if marking occurs when a cat is seen outside, stick these windows off. Possibly medication can be given to reduce stress. It is essential to clean the areas where the cat has marked well (e.g., sequentially with water, soap, and fire spirits). In general, it appears that a cat that sprays a lot can unlearn this in a completely different environment. Consult with a behavioral specialist.