Have you tried adding a second litterbox?  Some cats do not like to urinate
and defecate in the same box.  Have you tried uncovering the litterbox?
Have you tried other types of litter?  There's also a litter called Cat
Attract that I have heard many people have had success with.  Most
importantly, have you taken him to the vet to check for a Urinary Tract
Infection?

Has he been to the vet, in case the inappropriate peeing is due to a urinary
tract infection?  Peeing outside of the box (on occasion, not necessarily
all of the time) is a symptom of a UTI.  So that'd be the first step to
take, in case it's medical Vs. behavioral - or if it's at least partially
medical.  A round - or two - of antibiotic(s) would clear it up if he has an
infection.

From your description I'm not sure if he's just peeing outside of the box,
&/or spraying (marking).

Cathy

I cannot think of getting rid of my beloved Rutherford the Brave.
Is there something I can get to spray in the house to either deter him
from marking, or to cover up the scent of his urine?  I know cat urine
to be one of the most horribly smelling things on this planet...

jimmy

One, take him to the vet to check for a urinary tract infection. They will pee
right in front of you when they have an infection. They're trying to tell you
that they're sick. If he's okay, here are some things I learned about spraying.
Your cat probably also feels insecure about your dog because they don't get
along. Your cat therefore is leaving little memos around the house telling
everyone that he lives there also. Below is something I posted earlier. In it
my cat Patches felt insecure around Mimi. In your situation, your dog is Mimi
and your cat is Patches.

I just spent $395 to go to a cat behavioral psychologist. Patches spraying was
driving me nuts. Last week he peed on the bed and sprayed the side of it. He
does not have a urinary tract infection. He only sprays near where Mimi likes
to sit and sleep so I knew it had something to do with her. They don't hate
each other but they're not good friends either.

The doctor spent two hours counseling me about Patches and Mimi so he could
understand why Patches was spraying. Patches was spraying because he's upset by
outdoor cats spraying the outside of the house. He's also not that comfortable
with Mimi. I thought I'd share this counseling session so that it might help
others (and they could save the $395!) So far I've done everything the doctor
said to do and Patches hasn't sprayed. It's only been a week. I'll keep you
updated in another few weeks to see if he really stops spraying for good. I
transcribed the below from the big behavioral prescription he gave me.

Dr. Polsky http://www.drpolsky.com 

Behavioral therapy interview

Problem: Cat is spraying to communicate. He is upset by other cats spraying the
outside of the house. He is upset by other inside cat. He is basically not very
confident psychologically so he sprays.

Solution: Keep outside cats away from the house so they can't spray the
exterior doors and upset him. Make spraying cat feel more comfortable with
other cat. Make it so he doesn't have to compete for resources, has his own cat
tree, extra litter boxes. Make it so he eventually will like the other cat more
by associating closeness to the other cat with positive things such as food,
brushing, play time. Make previously sprayed areas unattractive by cleaning and
making it impossible for him to spray there again.

A. Increase number of litter boxes from one to four so cat won't feel
competition for resources. Switch to sand litter which they both prefer. Keep
very clean. Two boxes in the living room, one in the office, one in the dining
room.

B. Keep music room closed. Cat was spraying in there and it's easy to block off
that room for the time being.

C. Feed both cats at very close distance, bowls touching. You may have to
slowly move the bowls together. This will make the sprayer associate the other
cat with good things such as food.

D. Brush cat at close distance to other cat so he will associate good things
with the other cat. He likes being brushed.

E. Teach cats to come in command for food treat together so they associate each
others presence with good things.

F. Mutual play sessions in each others presence. Include both of them playing
with a toy.

G. Mutual grooming. Hold finger with petromalt or other yummy food on finger.
Put finger near other cat. Let spraying cat lick food off finger very close to
other cat. Eventually put finger on other cat then put food on other cat so he
can lick off. This should encourage mutual grooming.

H. Provide ample marking locations for spraying cat so he can rub his face and
scratch on posts or brushes to mark using his scent glands instead of spraying.

I. Add a cat tree for spraying cat in location that doesn't have view of
street. View of street may upset him if he sees other cats or dogs. He needs
his own cat tree to sit on because other cat is on other tree.

J. Abut previously marked areas with upside down carpet runners with the sharp
plastic points up so he can't back up and spray areas again.

K. Keep outside cats away from exterior of house with ultrasonice devices,
upside down carpet runners so they can't spray exterior doors and mousetraps
(won't hurt cats, just scare them.)

L. Use Feliway where he has sprayed before. Clean sprayed areas with
anti-icky-poo enzymatic cleaner. Spray "No Mark" by Nala Barry Laboratories in
California over the areas to keep him from respraying.

M. Drug administration. buspirone (Buspar Rx)
5-10 mg. BID (2.5 x day).

http://www.petalia.com.au/templates/StoryTemplate_Process.cfm?Story_No=305
http://www.hssv.org/behavior/cat/cat_spray.htm
http://www.ivis.org/advances/Behavior_Houpt/seksel/chapter_frm.asp?LA=1

The first step is to go to the vet and rule out a medical cause.

You start with a visit to the vet to rule out a medical issue as the
root cause for this.

Once having done that, you can then proceed a little less in the dark.

To take action without getting a clean bill of health first IS
proceeding in the dark.

Explain the whole thing to the vet, if there are no medical issues then
perhaps the vet can offer suggestions.

Have you seen your vet ?

Owen

I was thining today ato work about this post - and I am wondering if
maybe he is hungry or something - could that be a possibility?

I feed him half a can of Friskees in the morning, and he has dry food
all day.

how often do you feed your cat?