  In this article we provide explicit computations of the quantum corrections
to the lightest CP-even Higgs Boson mass in the real version of the Minimal
Supersymmetric Standard Model. We compute the contributions coming from the
SUSY-QCD sector with a precision of three loops at order
$O(\alpha_t\alpha_s^2)$. The renormalization procedure adopted is based on the
dimensional reduction scheme in order to preserve supersymmetry to all
perturbative orders. The calculation extends the region of validity of previous
studies to the whole supersymmetric parameter space. The involved master
integrals have been computed by exploiting new proposed approaches based on the
dispersion relation techniques for the numerical calculation of three-loop
vacuum integrals with arbitrary mass scales.
