  This talk is based on work performed with Graham Ross and is a very concise
summary of our soon to be published paper. Here we present a revision of the
analysis of sphaleron baryon-number violating processes in the standard model
including lepton-mass effects. We find the surprising result that a GUT-scale
matter-asymmetry can survive the $B$ and $L$ violating sphaleron interactions
even though ($B- L$) is conserved and equals zero for all temperatures. We
extend the analysis to cover the minimal supersymmetric standard model (MSSM).
As a new result we present the MSSM analysis below the temperature of
electroweak breaking and for $B-L=0$ at all temperatures
