There is a variety of possible causes and remedies.
But prevention is even better.
Most cat owners will at some point face the issue of having to toilet train cats.
When adopting young kittens this is the first thing to do.
The reason is that it's easiest to litter train a cat while it's young.
But this isn't always possible.
For example, you might have to move from a place with outdoor access for you cat to one without it.
This would bring up the issue of litter training an adult cat.
This can be done successfully with just a little patience.
On the other hand, sometimes a well-behaved cat will start avoiding its box.
Health: As with any change in a cat's behaviour, a responsible owner should consult a vet immediately.
Some of the possible medical causes are very serious, such as: colitis inflammatory bowel disease diabetes mellitus hyperthyroidism kidney disease liver disease feline lower urinary tract disease arthritis anal sac disease The discomfort and/or pain associated with such health problems can make the cat think that it's litter box is the cause.
It will try to get relief by going elsewhere.
Any treatment for the underlying health problem would automatically take care of the litter box problem too.
On another note, a number of these diseases are quite advanced by the time a cat owner can notice anything.
For that reason alone, no time should be lost in seeking veterinary treatment.
If a cat is an un-neutered male, he is most likely just marking his territory.
(Females are less notorious, but they might also display the same behaviour.
) Neutering should put a quick stop to the problem.
On the other hand, if left for too long, a cat might just continue spraying out of habit, even after he's been neutered.
Neutering (and spaying) also helps reduce the overpopulation and subsequent suffering of so many other cats.
Stress/Change: If a cat suddenly starts "thinking outside the box" after moving into a new home, there might be more than one cause.
Possibly there was feline resident there before.
In that case the newcomer is just superimposing its own scent.
Specialized enzyme based cleaners will dissolve both traces of the previous cat and the fresher urine.
This is important because cats like to go back to the same spot if they can smell it.
Or it could simply be the stress of the actual move.
Felines, just like humans, don't particularly enjoy the upheaval.
One should also always make sure that the cat knows where the litter box is in the new place.
A lot of affection and possibly some natural calming remedies can help a cat settle a lot more quickly.
Again, removing all traces of urine is essential to preventing repeat performances.
Other sources of stress can be the loss or addition of a partner or other family member, or of course a pet.
In all of these cases affection and patience will go a long way.
Litter/ Litter Box: The litter box itself and it's content can have a lot to do with a cat's rejection.
Many of the fancier types of boxes are mainly created for the benefit of the human.
Enclosed litter boxes might not only be awkward to use for some cats, but they can also trap and magnify odours.
Regular cleaning is no less important with closed litter boxes, just because the human can't smell them from the outside.
If anything it's even more important.
Otherwise it's extra unpleasant for the cat and might provide an excuse for going elsewhere.
Similarly to box designs, scented types of cat litter might appeal more to the human than the cat.
To a cat's refined sense of smell such artificial scents might just be overpowering and off-putting.
It's recommended to try a few natural neutral types of litter instead.
Usually at least one of them will be received much better.
On the other hand, the problem might not be any of the above.
It could be just what happens to all of us when we see and smell a neglected public toilet.
We'll give it a miss and go somewhere else.
Even the most conscientious cat people might sometimes forget to clean out the litter box.
Keeping on top of it can make all the difference.
Sometimes cats that spray might need a little refresher course.
There are fairly extensive courses on how to litter train a cat.
The basic concept is to shut the cat into a room with its clean litter box until it uses it.
Sometimes a whole day or several sessions are required.
Rewarding the correct behaviour will reinforce it in the cat's memory.