  We analyze the effects of a doubly charged vector bilepton as well as exotic
quarks with charge 5/3 e and -4/3 e on light by light scattering. We consider
mass values in the range 0.3--1 TeV, which would be reached at the planned
future linear colliders. It is found that such exotic particles, especially the
doubly charged vector bilepton, give raise to remarkable deviations from the
standard model cross section. The virtual effects arising from these particles
would provide an indirect test to a particular model which is based on the
SU_c(3) X SU_L(3) X U_x(1) gauge symmetry, known as the 331 model, where such
particles are a natural prediction.
