  Parity-violating deep inelastic scattering (PVDIS) has been proposed as an
important new tool to extract the flavor and isospin dependence of parton
distributions in the nucleon. We discuss finite-Q^2 effects in PVDIS
asymmetries arising from subleading kinematical corrections and longitudinal
contributions to the photon-Z interference. For the proton, these need to be
accounted for in order to accurately extract the d/u ratio at large x; for the
deuteron they are important to consider when searching for evidence of charge
symmetry violation in parton distributions or signals for physics beyond the
standard model. We further explore the dependence of PVDIS asymmetries for
polarized targets on the u and d helicity distributions at large x.
