carpet ...

This is a neutered cat, right?

I'd try putting a liter box right on that spot.  Even if it's in
the middle of the room...just temporarily.  It seems he has
adopted it..what you need to do is physically prevent him
from being able to use it long enough for him to "un-adopt" it.

I'm not sure why he would be doing this.  Doesn't seem like
it's stress if he did it calmly right in front of you.  I have to
assume he is altered and that you have ruled out a medical
problem.

Do you have other cats?  Were they near the liter box
when he sprayed?

AG

We're dealing with cat peeing problems, also.
Here are the steps we are taking this week (cat was just at the vets on
Thursday)
1)  cat is now on .5 mg of prozac (real people prozac!!) for anti-anxiety
2) we bought plastic carpet runner and have put it in places kitty has peed
(sharp pointy things side-up).
This stuff is pretty cheap - only $1.50 a linear foot.  We think we're going
to have to carpet the whole house with it and only leave paths for us to
walk on!!
As for the nature's miracle - I couldn't get it to work, either. I use 'Get
Serious' which I found on the web. It works pretty well. It does stink when
we apply it - its re-activiating any urine that has dried. I scrub it in
really well - it gets real foamy -  then let it sit for about 15 minutes,
then blot up as much as I can - until the carpet feels dry. I cover the area
so the cat can't return (I usually prop some pieces of wood up on some
veggie cans)   I then keep a fan running on it for a couple of days to give
it a good chance to dry.

The cat we are having problems with was indoor-only.  We started letting him
and his brother out just last Monday (they have 3 older step-brothers to
watch them outside, along with us). We have seen a huge change in their
confidence level, and they are much more affectionate towards us.  Plus, the
litter boxes have been emptier.

I hope this helps. It is such a big job keeping up with them.

I use a small bissell carpet cleaner. First I put water on the area with carpet
cleaner, then I suck that up with the bissell. Then I do it again. After I've
sucked up all the urine I can, I let it dry then use nature's miracle. It will
still smell like cat urine for a little bit. Then I spray no mark.

You could also try putting a carpet runner upside down on that spot then it
will be physically impossible for him to  pee there. Or you could put a heavy
large object over the spot. I would also give him an extra litter box.

If that fails, try the drugs. I'd also get a cloth collar, spray feliway or no
mark on the collar, let it dry then put it on him.

Because he did it right in front of you he is trying to send you a message. My
cat does this when he has a urinary tract infection but I think it may be the
dog that your cat has issues with because you said you cat is healthy.

The only way you're going to shape a cat that old, assuming good health, is
with a water pistol & a very loud & angry voice/noise.

Think like a cat, and you're half way there!

First thing to try, would be to banish him from that room for a month, and
see if he does it elsewhere. If not, there's an unquantifiable cat quality
about the particular spot that should respond to the treatment below,
suggested. Good luck!

You'll have to be his shadow for quite a while, and combine the three
whenever it looks like he's about to do the business. Don't worry, he won't
take it personally, since you'll only do it when he's spraying.

It won't take too many times of you catching him before he learns, cats are
quick learners. If he transfers the behaviour, perhaps there's a
personality/dominance issue to address.