> I think i've found a way, please tell me if you see any disadvantage > (anyway, i think that an \onslide-something command that eats its argument > but reserves space would be useful, but i have no idea if it would be > difficult to implement): That is \onslide. And slide 1 and 3 do different things. Look at 'another item'. So, it's not clear what you want. -Hendri.