  We investigate the parton distribution functions (PDFs) of the pion and kaon
from the eigenstates of a light-front effective Hamiltonian in the constituent
quark-antiquark representation suitable for low-momentum scale applications. By
taking these scales as the only free parameters, the valence quark distribution
functions of the pion, after QCD evolving, are consistent with the E615
experiment at Fermilab. In addition, the ratio of the up quark distribution in
the kaon to that in the pion also agrees with the NA3 experimental result at
CERN.
