  We derive strong contraints on the Yukawa couplings and the vacuum
expectation value in the singlet majoron model, taking into account the
possibility of a small gravitationally induced mass for the majoron. If the
present baryon asymmetry was created earlier than at the electroweak phase
transition, then to preserve it from the combined effects of lepton number
violating interactions and electroweak sphalerons, we find that stringent
constraints on the Yukawa couplings, $h < 10^{-7}$, and the majoron scale, $v_s
< v_{EW}$, must be satisfied. We also carefully rederive baryogenesis bounds on
neutrino masses, finding that in general they apply not to the masses
themselves, but only to related parameters, and they are numerically somewhat
less stringent than has previously been claimed.
