  We analyze the effective 3 dimensional theory previously constructed for the
MSSM and multi-Higgs models to determine the regions of parameter space in
which the electroweak phase transition is sufficiently strong for a $B+L$
asymmetry to survive in the low temperature phase. We find that the inclusion
of all supersymmetric scalars and all 1-loop corrections has the effect of
enhancing the strength of the phase transition. Without a light stop or
extension of the MSSM the phase transition is sufficiently first order only if
the lightest Higgs mass $M_{h}\lsi 70$ GeV and $tan\beta\lsi 1.75$.
