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Though the cat is renowned for its cleanliness, peeing at home outside the litter-box is the most common behavioral problem reported in cats and the number one reason for owners giving the cat up.

Before examining the different behavioral reasons it is most important to rule out any medical problem, and first and foremost "Feline Lower Urinary Tract Disease", which signs are straining to urinate, excessive licking of the genital area, bloody urine and peeing out of the box. 

So a cat peeing outside his litter box should first undergo a thorough veterinary exam.

Territorial Marking – mostly in intact males

Cats use urine and feces as a means of communication with other cats. When they leave their mark they are telling other cats: "this land is mine!" Stress and changes such as a new pet in the house, a guest, moving to a new home, invasion of stray cats to the cat's back yard, even a change in the furniture setting can trigger the cat's need to re-mark his territory. 
Typical marking behavior would include:·
-        Urinating on vertical surfaces
·        Urinating sometimes in and sometimes out of the box ·        Defecating in the box but urinating outside·
-        Sprayed area is near door or window.
-        It seems as if the cat is urinating on purpose   (actually,he is urinating out of nervousness because he can sense his owner is upset with him)· 
-       Cat is marking the owners laundry or beddings·
-       Cat is urinating in same places.

If some of these signs apply it's best to find the reason for the cat's stress and eliminate it, or treat with anti-anxiety drugs. 
To deter the cat from going back to the places he used to mark, clean the surfaces with a strong detergent. 
It's most important to castrate these cats because the hormonal impulse to mark is very strong.

Avoiding the litter box

Another set of reasons for cats choosing to relieve themselves outside the litter box is repulsion from the box itself. 
The reasons for this behavior are many and varied: the box is dirty or smelly, the box is situated in a place that stresses the cat, the cat had a bad experience while previously using the box and now he associates the box with something negative, the box is used by other (higher ranking) cats, etc'.

In these cases there is no vertical spraying and the cat gives feces outside the box as well. 

Cats with this problem need "re-educating". 
First put an additional box in a different location to the first one. In multiple cat households the number of boxes should exceed the number of cats by one. Also, separate the litter box from the food bowl – cats usually don't want to use their eating area as a toilet. 
And finally – replace the cat litter. 
If nothing helps, limit the cat to a small space with the litter box in it. When he re-uses the box you can gradually enlarge his territory.

We are always here for questions and instructions. 

Good luck!