  We study a nonlocal generalization of two flavor fermion mixing and compute
the transition probability by means of the path integral formalism. In our
treatment, we delocalize only the mixing term, and consider a perturbative
interaction with a small mixing angle. The oscillation formula derived reduces
to the correct local form when the appropriate limit is considered. We apply
our formalism to some string-inspired delocalization kernels and discuss the
phenomenological deviations from the local theory.
