  We report on a two-loop supersymmetric contribution to the magnetic moment
(g-2)_mu of the muon which is enhanced by two powers of tan(beta). This
contribution arises from a shift in the relation between the muon mass and
Yukawa coupling and can increase the supersymmetric contribution to (g-2)_mu
sizably. As a result, if the currently observed 3 sigma deviation between the
experimental and SM theory value of (g-2)_mu is analyzed within the Minimal
Supersymmetric Standard Model (MSSM), the derived constraints on the parameter
space are modified significantly: If (g-2)_mu is used to determine tan(beta) as
a function of the other MSSM parameters, our corrections decrease tan(beta) by
roughly 10% for tan(beta)=50.
