For me, I never buy cat litter/pan. All my cats do their business in the toilet. We actually trained the mother and the rest, just follow. But, as Rozita said, it took a lot of effort..and of course, we have to be very very patient. If you start to introduce the kitties to the toilet business since they're very young, then it would be easier. They will normally do it on the floor first. You have to scoop the "poo" & place it nearer & nearer to the toilet bowl (if the kitty do it quite far from the bowl) or just put it inside the bowl & leave it for a while. Then, take the kitty to smell it. Wash clean the floor before u do that. Well, that's how i trained the mother.

And, when my parents bring along my kitties (they're staying with my parents now) when they visit me, all my kitties still know how to use the toilet...though at first it was hard to get them to "pee" & "poo" because they're not used to the environment. My mom has to massage their stomach so they can let go. However, when they've felt comfortable, they just go into the toilet & do their business.