Is there anything that *he's* doing differently? Does he seem to be trying to go more often? Is he crying at all when he tries to go? Have you been scooping regularly, and if it's not the scoopable kind, have you put fresh litter in the box?
Um.. Is there anything that's changed about his environment.. i.e., have you moved his food, water, stopped playing with him, changed your or his schedule in any way, added another animal to the house, painted, is there a new person living there... *any* of that might affect it.
Is it only pee or is it pee and poo? Does there seem to be any pattern to what he's doing, a favorite type of surface.. is it close to the litter box but not in it..
How old is the kitten? Does he have diarrhea? Have you noticed any change in his eating or drinking habits?
You may want to take the cat to a vet and make absolutely sure that this isn't a medical problem. Medical problems can cause him to avoid the box. If he's crying when he potties, then it's a very good possibility that he's avoiding the box due to a medical issue.