  D.Happel and L.Unger defined a partial order on the set of basic tilting
modules. We study the poset of basic pre-projective tilting modules over path
algebra of infinite type. First we will give a criterion for Ext-vanishing for
pre-projective modules. And by using this we will give a combinatorial
characterization of the poset of basic pre-projective tilting modules. Finally
we will see a structure of a pre-projective part of tilting quivers.
