  We pursue a phenomenological study of higher twist effects in high energy
processes by taking into account the off-shellness (virtuality) of partons
bound in the nucleon. The effect of parton off-shellness in deep inelastic
ep->eX scattering and the Drell-Yan process (pp->l+ l- X) is examined. Assuming
factorization and a single-parameter Breit-Wigner form for the parton spectral
function, we develop a model to calculate the corresponding off-shell cross
sections. Allowing for a finite parton width of the order of 100 MeV, we
reproduce the data of both DIS and the triple differential Drell-Yan cross
section without an additional K-factor. The results are compared to those from
perturbative QCD and the intrinsic-kT approach.
