  We reconsider the GUT-baryogenesis mechanism for generating the baryon
asymmetry of the Universe. The baryon asymmetry is produced by the out of
equilibrium decay of coloured Higgs bosons at the GUT scale, conserving B-L. If
neutrinos are Majorana particles, lepton number violating interactions erase
the lepton number excess, but part of the baryon asymmetry may be preserved,
provided those interactions are not in thermal equilibrium when the sphaleron
processes become effective, at $T \sim 10^{12}~ GeV$. We analyse whether this
mechanism for baryogenesis is feasible in a variety of GUT models of fermion
masses proposed in the literature, based on horizontal symmetries.
