How many litter boxes do you have?
We have two. I know the rule of thumb is one box per cat plus one extra but we started out with just two cats and the two boxes worked fine for them. Then we got the additional two cats to bring the total to four and didn't put out additional litter boxes until they'd been with us for about two weeks. We put out two more boxes but none of them used them. At all. So we figured they were fine with the two original ones.

Quick recap. We've had our two boys since October 2004. We got the girls (on a whim) April 2005. I was four weeks pregnant when we got the girls (didn't know it yet). From April '05 to July '05, things were fine. Then Josh and I took the boxes outside to clean and disinfect and Josh decided to put them in another location (just inside a doorframe from where they had been, so it's not like they were far away. We showed all the cats the new location. And then the pooping outside the litter box began, where the litter boxes had been. Nothing we did stopped it, so we moved the boxes back to that location thinking that's where they liked it. The pooping outside the litter box continued. We took them to the vet. They all got clean bills of health. We tried Feliway, different litter, cleaning it out often, not cleaning it very often, different depths of litter. The pooping outside continued until around February '06 and stopped, amazingly enough, for about 6-7 weeks. Then I shampooed the area of the rug in preparation for my son's baptism and within hours, there were several different poops on the carpet.

What type of litter? Do they all use the same litter? Do you use scented litter?
We use FreshStep. It's in both litter boxes. I'm not sure if it's scented or not. We just use the FreshStep with the blue crystals in it. Always have.

What depth of litter? Are all litter boxes the same?
The litter boxes are both the same - the domed "booda" ones with the "steps" going up into it. We've also tried taking the tops off in case they didn't like it. Didn't stop anything.

Have you tried separating the litter boxes so someone could have a little privacy?
They're domed, so they have privacy. And moving them is what originally began this mess so no, we haven't moved them since putting them back where they were.

Is it possible one of your cats is harassing the others while using the litter box?
I suppose it's possible, but not that I've noticed. As I said above, the boxes are domed and there is only room in there for one cat at a time, so there is limited means of harrassment.

Are they located near anything noisy or scary?
Nope, they're in a quiet alcove in our basement.

I apologize if you've already been through this, but it sounds like you need to make sure you've covered everything.
No worries at all. I appreciate the help.

Finally, are you willing to consider "drastic" litter box actions?
I guess we will if we need to, but you'll have to forgive me if I sound skeptical of anything that may be suggested. I just feel like we've tried it all and nothing is working.

That said, the pooping (and peeing) immediately outside of the litter box area is annoying. What has me extremely concerned is that Kimi (at least - she is the only one I've caught in the act) has begun to pee in the kitchen, which on an entirely different level of the house. It's spreading. What if it spreads to the living room so that carpet gets ruined? Or our bedroom, so that carpet gets ruined? I hate that the bit of carpet in the basement is ruined but that's not in a heavily trafficked area and out of view to guests completely. The living room isn't. Our bedroom isn't. Aidan's room isn't.

I'm just very, very frustrated. Kimi didn't pee there this morning but that's because I sprayed Chlorox bleach there and some orange-scented cleaner and left it there so it was wet. But I can't do that all the time - the floor in the kitchen is pergo and leaving it constantly wet makes it buckle and bubble (we learned that from a leaky fridge).