How recently did you aquire these hammies? When I got my hamster Ritz, the woman who sold him to me told me that I should not pick him up for three days to let him settle down. I followed these rules, but my little sister did not! After one day she stuck her hand in and he bit her, pretty hard too! Anyway, I am not sure if this is your case, but if it is, you might want to just leave them alone for a while and let them get used to their surroundings. Ritz never bit again for the rest of his life (well, except once when my cousin was poking him hard on his poor little head while he was trying to sleep - can you blame him!?). Well, good luck with your hamsters! They are such wonderful pets, I really miss my poor Hammie sometimes! He died two years ago but I still miss the little guy, what a sweetie!