  We investigate the possibility that baryogenesis occurs during the weak phase
transition in a minimal extension of the Standard Model which contains extra
neutral leptons and conserves total lepton number. The necessary CP-violating
phases appear in the leptonic Yukawa couplings. We compute the CP-asymmetries
in both the neutral and the charged lepton fluxes reflected on the bubble wall.
Using present experimental bounds on the mixing angles and Standard Model
estimates for the parameters related to the scalar potential, we conclude that
it seems unlikely to produce the observed baryon to entropy ratio within this
type of models. We comment on the possibility that the constraints on the
mixings might be naturally relaxed due to small finite temperature effects.
