  Reasonably large relic neutrino asymmetries can be generated by
active-sterile neutrino oscillations. After briefly discussing possible
applications, I describe the Quantum Kinetic Equation formalism used to compute
the asymmetry growth curves. I then show how the basic features of these curves
can be understood on the basis of the adiabatic limit approximation in the
collision dominated epoch, and the pure MSW effect at lower temperatures.
