  Motivated by the strong experimental evidence of large nu_mu - nu_tau
neutrino oscillations, we study existing constraints for related mu - tau
flavor violation. Using a general bottom-up approach, we construct dimension-6
effective fermionic operators whose coefficients encode the scale of new
physics associated with mu - tau flavor violation, which is a piece in the
puzzle of the origin of neutrino oscillations. We survey existing experimental
bounds on this scale, which arise mostly from tau and B decays. In many cases
the new physics scale is constrained to be above a few TeV. We also discuss the
operators which are either weakly constrained or, at present, subject to no
experimental bounds.
