  We propose a new implementation of target mass corrections to nucleon
structure functions which, unlike existing treatments, has the correct
kinematic threshold behavior at finite Q^2 in the x -> 1 limit. We illustrate
the differences between the new approach and existing prescriptions by
considering specific examples for the F_2 and F_L structure functions, and
discuss the broader implications of our results, which call into question the
notion of universal parton distribution at finite Q^2.
