  We present the two-loop SUSY-QCD corrections to the effective bottom Yukawa
couplings within the minimal supersymmetric extension of the Standard Model.
The effective Yukawa couplings include the resummation of the non-decoupling
corrections Delta m_b for large values of tg(beta). We have derived the
two-loop SUSY-QCD corrections to the leading SUSY-QCD and top-induced
SUSY-electroweak contributions to Delta m_b. The scale dependence of the
resummed Yukawa couplings is reduced from O(10%) to the per-cent level. These
results reduce the theoretical uncertainties of the MSSM Higgs branching ratios
to the accuracy which can be achieved at a future linear e+e- collider.
