  The experimental discovery of large nu_mu-nu_tau mixing indicates that
analogous mixing in the charged lepton sector could be substantial. We consider
the possibility that if a high intensity muon beam, perhaps at the early stages
of a muon or neutrino factory, strikes a nuclear target, then conversion of
some of the muons into tau leptons could occur (similar to the conversion of
muons to electrons at MECO). Using current experimental limits on rare tau
decays to bound the size of the relevant operators, we find that a 50 GeV muon
beam, with 10^20 muons on target per year, could yield as many as 10^7 mu + N
--> tau + N events per year. Backgrounds could be substantial, and we comment
on the possibility of detection of this process.
