  This note summarises recent progress in the formulation of flavour mixing and
oscillations in pseudo-Hermitian quantum theories with non-Hermitian mass
mixing matrices. Such non-Hermitian quantum theories are made viable by the
existence of a discrete anti-linear symmetry of the Hamiltonian, which ensures
that states have real energies. We describe oscillation and survival
probabilities in a non-Hermitian two-state quantum mechanical system that are
consistent with unitarity, and highlight features of these pseudo-Hermitian
flavour oscillations that are unique compared to their Hermitian counterparts.
