My bun does that sometimes too. It scares theliving daylights out of me cause I'm not sure what causes it. Hedoesn't seem to be sick and the only times he's ever done it was onetime when I picked him up and handed him to someone else and one timewhen I let him roam on my sister's bed (he was laying down, breathingreally fast-like---I lifted him up and there was a HUUUUUGEEEE, I meanHUGE puddle of pee!). Neither times was he really exercising before, orwell not enough to what I think would be exerting for a rabbit. And nowhe exercises more and doesn't ever breath hard anymore (that I noticeanyway). It worries me too! :shock: