Horizontal symmetries,dynamical symmetry breaking and neutrino masses

We study experimental and theoretical constraints which can prevent the introduction of horizontal gauge ssymmetries. To allow for the possibility of dynamical symmetry breaking, we restrict the symmetry breaking interactions to have the quantum numbers of spin-zero bound states of the fermions in the theory. Under these circumstances we find that horizontal interactions, which do not violete any of the present bounds on flavor changing processes, are only allowed if the symmetry breakdown introduces a large Majorana mass for the neutrinos. Some phenomenological consequences of this result are discussed.