I recently had a problem with the new member of the family, Penny, urinating outside of the box.
She'd go around my room, in my clothes, and sometimes, just outside of the box. I knew she was new to the house, so maybe she was just stressed.
I did a couple of things that helped 100%, though I'm not sure what really did it. First, I changed the litter to Cat Attract.
I was skeptical about a litter actually helping this problem, but as soon as I put the litter in the box, even before it was back in it's normal place, she'd jumped in to dig around.
The litter is expensive, but it offers a 100% litter box usage guarantee, so I bought it anyway. The other thing I did was I bought a synthetic feline pheromone diffuser.
It's supposed to calm stressed cats. As soon as I plugged it in, my other kitty, Moe, sat right next to it.
I'm not sure which one of these products did most of the work, but Penny has been using her litter box since I took action.
I might buy some cheaper litter and mix it with the Cat Attract, because it really is expensive, but I have to have it.