  Muon lepton flavor processes are reviewed in connection with search for
physics beyond the standard model. Several methods to distinguish different
theoretical models are discussed for $\mu \to e \gamma$, $\mu \to 3 e$, and
$\mu - e$ conversion processes. New calculation of the $\mu - e$ conversion
rate is presented including a Higgs boson mediated effect in the supersymmetric
seesaw model.
