  We study assignments of the hypercharge and baryon minus lepton number for
particles in the $E_6$ grand unification model. It is shown that there are
three assignments of hypercharge and three assignments of baryon minus lepton
number which are consistent with the Standard Model. Their explicit expressions
and detailed properties are given. In particular, we show that the $U(1)_{B-L}$
symmetry in $E_6$ cannot be orthogonal to the $SU(3)_R$ symmetry. Based on
these investigations, we propose an alternative SU(5) grand unification model.
