  We investigate the possibility that quarks and leptons are unified at a low
energy scale much smaller than the grand unified scale. A simple theory for
quark-lepton unification based on the gauge group SU(4)_C X SU(2)_L X U(1)_R is
proposed. This theory predicts the existence of scalar leptoquarks which could
be produced at the Large Hadron Collider. In order to have light neutrinos
without fine tuning, their masses are generated through the inverse see-saw
mechanism.
