We show that in the presence of primordial magnetic fields, it is possible to produce a large enough amount ofCPviolation to possibly explain the baryon asymmetry of the universe. This can happen during the reflection of fermions off the true vacuum bubbles nucleated during a first order phase transition. The chiral nature of the fermion coupling to the background field in the symmetric phase can be used to construct two-fermion interference processes in analogy to the Bohm-Aharanov effect. By describing the transport of theCPasymmetry into the symmetric phase, it is possible to generate a baryon to entropy ratio&rgr;B/s=(3−6)×10−11,which is close to the observed value based on uncleosynthesis considerations. ©2001 American Institute of Physics.