  We calculate the effects of next-to-leading order perturbative QCD as well as
of the quark transverse motion and off-shellness on the Drell-Yan process cross
section. By studying the s->infinity behaviour of the cross section in these
approaches, we find that the effects of quark off-shellness and intrinsic-k_T
parametrize those of higher twists. In particular, the off-shellness of partons
generates part of the K-factor type corrections to the leading order cross
section. Higher twist contributions to the p_T-spectrum of the Drell-Yan pairs
are found to be large for presently accessible energies. The evolution of quark
off-shellness distribution with the hard scale is also studied.
