Cats will occasionally urinate outside of the litter box, so if you're having a problem with your cat you must determine if the cause of the "accident" is physical or emotional. If you have many cats, your cat may be spraying an area to mark it as his own. Cats communicate with different scents in their spray, and your cat may simply be sending a message to the other cats. You must also ensure that there is no competition over the litter boxes and that the litter is changed regularly. If the problem is occurring frequently, take your cat to the vet to make sure he doesn't have a physical problem such as kidney stones.
Make sure all your cats are sterilized. A male cat who has not been neutered will spray surfaces with a small amount of urine to let females know he is active and available. While male cats who have not been neutered are most likely to spray, females can spray -- as can cats of either gender who have been neutered or spayed. Spray is usually deposited on vertical surfaces, and you will see your cat back up to the surface with his tail in the air. Spray contains chemicals that convey messages to other cats -- such as telling other cats to stay away -- but that smell very pungent to humans. If your cat is spraying around the house, you will probably notice each spray is a very small amount of urine. This is because your cat can spray small amounts many times in many different areas. Having your cats sterilized will cut down the need for certain kinds of spraying, such as spraying that tells other cats your cat is sexually active and available.
Have one litter box for each cat in your house, and one extra. Cats are territorial and independent, and some cats will refuse to use a litter box that smells like another cat. If you have four cats, your house should have five litter boxes. Clean each litter box every day and completely change the litter once a week to make sure your cat's powerful sense of smell is not overwhelmed by odors. Some cats will refuse to use a litter box that smells like urine and feces. If you can smell your litter boxes, your cat is certainly overwhelmed by the odor and may simply be relieving herself in an area that does not smell foul to her.
Ensure each litter box has two escape routes, and that each box is accessible to cats with limited mobility. Senior cats and cats that have been injured may have trouble getting into and out of litter boxes that have small entry ways or entrances that are high up. Get plain old litter boxes without lids or doors if you have cats that may have physical problems accessing the litter box. Also ensure your cats cannot be intruded upon or trapped by other cats while using the litter box. Like humans, cats prefer peace and quiet while relieving themselves. A cat who feels constantly invaded or intruded upon may refuse to use the litter box, and will seek out quieter spots.
Create spaces where your cats can get away from each other. Cats are for the most part lone creatures, and do not enjoy constant company. Clear shelves for your individual cats to perch on, or place small tables by windows so your cats can have some alone time. Cats who feel their territory is being encroached on will spray "Stay away" messages to other cats -- all over your house.
Clean any spray or urination with non-ammonia cleaner. Cat urine contains ammonia, so if you use an ammonia-based cleaner your cats will continue to be attracted to the area. Use an enzymatic cleaner for the best results.
Be vigilant if there is change in your household. Cats do not like change, and will spray anxious messages or urinate outside of the litter box due to panic. If you are going on vacation, moving or getting a new baby or pet your cat may react with "accidents." Be patient -- your cat should adapt to the change within a few days. If your cat does not become accustomed to the change, he may be excessively stressed out or anxious and may require a trip to the vet. Behavioral medications can help in these instances.
Take your cat to the vet if the problem persists, your cat appears to be straining to urinate or cannot control her urination. If your cat is ill, she may not be able to control her bladder and may urinate frequently in secluded areas. If your cat appears to be in pain or makes howling sounds while urinating she may have a urinary tract infection (UTI), kidney stones or feline cystitis -- an inflammation of the bladder. If there is blood in your cat's urine or you notice any of these symptoms, take her to the vet at once. Inflammation of the bladder can be life-threatening, and any of these conditions are painful for your cat. Your cat may need medication or surgery to treat the condition.