Pion structure function based on a Bethe-Salpeter vertex function

The structure function of the pion, which can be related to a suitable Drell-Yan process, is calculated in terms of a null-plane formulation of the qq̅ wave function in a QCD-motivated Bethe-Salpeter (BS) model. This represents a first "high energy" test of the BS model whose "low energy" successes include an excellent description of the hadron (qq̅ ,qqq) spectra. The calculated structure function which excludes sea or gluon effects (for a clean identification of the valence quark contribution), follows rather well the data of the NA3-collaboration beyond the domain of sea-effects (x>0.2) with no adjustable parameters beyond the basic constants such as masses. The theoretical significance of this basically non-perturbative result, vis-a-vis related approaches, is discussed