S.G.
go in check and make sure he's ok, check diaper and what not....and let him fit, if he spits up, put a blanket or something down on top of it to keep him from sleeping in it then walk away (was in morning or whatever). my daughter used to do that, and i can't tell you how many nights she screamed ALL NIGHT, at first it was a nightly issue, then as she "thought" it wouldn't get me (it was HARD listening to her blood curdling screams) it diminished into a little here and there, she's almost 8 and i havn't had a bed time problem at all since she was 2. i could tell her to go to bed in broad day light at lunch time, and she MIGHT tell me that she's not tired, but she'll at least go lay down and be quiet.
as long as your consistant and dont' show him that if he cries you'll come running it'll eventually stop but it's HELL at first: either give him hell and it'll stop or let him give you hell and eventually it'll get worse :)