  We discuss possible studies of parton distribution functions (PDFs) in the
nucleon and nuclei at the Japan Hadron Facility (JHF). First, the PDFs could be
investigated by the 50 GeV primary proton facility. The distributions at medium
x are determined, for example, by Drell-Yan measurements. Second, there are
feasibility studies to propose a neutrino factory within the 50 GeV proton
ring. If such an intensive high-energy neutrino facility is built, neutrino
reactions should be able to provide valuable information on the PDFs, whereas
the current structure functions have been measured mainly for neutrino-iron
reactions.
