  Higgs boson mass sum rules of supersymmetric models offer attractive targets
for precision tests at future muon colliders. These sum rules involve the gauge
boson masses as well as the masses of the Higgs boson states which can be
precisely measured in the $s$-channel production process at a muon collider.
These measurements can sensitively probe radiative corrections to the Higgs
boson masses as well as test for CP-violation and nonminimality of the Higgs
sector.
