Add more litter boxes. You should have one for each cat +one. Scoop them
regularly. Cats won't use dirty boxes.

Use a cleaner made for removing urine odor on the spots where the cats have
marked. It's important to get the odor out or the cat might use the same
spot again. You can do a Google search of this NG to find discussions about
what products people have found to work.

You can use a black light (they sell small ones at pet stores) to locate
spots where the cats have peed. Cat urine will "glow" under black light.

W

Hi Corey ,
 Are the cats are spraying up the furniture and walls?
     Alison

Sad to say, you may want to start with a very simple solution: more
litterboxes. Most of us have cats or know of cats that want to poo in one
box and pee in the other. Some cats simply won't pee in the same box they've
pooped in, and vice versa. The general rule is one box per cat, with one
extra for the picky cats. Also, the bigger the box, the better. A rubbermaid
flat container like you can find at Target or WalMart for about $7 is
excellent. Walls are about six inches high, few cats are going to get pee
over the side of it.

Keep trying different litter; there are a LOT of brands of scoopable stuff
out there. Note that a lot of cats don't like the scented stuff. It may
make -us- think it smells better, but it's a strong smell for the cats, and
it may turn them away from the box.

If you're using the scoopable stuff, aim for scooping at least once a day.
To make it easy, get a small bucket, plop a plastic grocery bag or small
trash bag in there, and scoop. Easy to tote, easy to empty. A few posters
here have cats that refuse to use the box if there's even one pee-spot in
it. Cats are tidy critters, and if I'm going to choose a different bathroom
stall because someone wasn't nice enough to flush their mess, I don't expect
my cat to be less fastidious than -I- am.

Also, consider the behavior aspects. Does this happen downstairs near
windows where Portia could be seeing other cats or dogs or finding something
to make her upset? She may have come back negative on a UTI test, but is she
perhaps incontinent (can't hold her bladder very long, or dribbles urine and
can't help it)? A lot of posters have advised Feliway, a pheromone product
that soothes cats (works for my sister's cat who sprays by the downstairs
windows). It can be pricey, but if it works, it's worth it.

Please post updates with what seems to be working or if there are any
changes in her behavior. Even the little things that may not seem to be
important can sometimes tell you a lot.

Good luck!

~K