Thanks Bev. When you talk to 4 different people you hear 4 different explanations. To me it doesn't sound like learned behavior either. One of the nurses said, because of his lung problems when his belly is full it presses against his lungs and that's why he's throwing up so much. Doesn't sound like that's the problem because when he got a lot less food (after he was used to getting much more) he did throw up a lot too. The pediatrician said he wants something in his mouth and this could be his way of doing that. Well, he's got nothing in his mouth after puking and he doesn't look happy either. Conclusion: still unknown why he does puke a lot. And I mean a lot! He was crying this afternoon because he was hungry, got his bottle and 10 minutes later we could mop it all off the floor. And he went to sleep with an empty stumach.