  We extend the already existing two-loop calculation of the effective
bottom-Yukawa coupling in the MSSM. In addition to the resummation of the
dominant corrections for large values of tg$\beta$, we include the subleading
terms related to the trilinear Higgs coupling $A_b$ and contributions induced
by the electroweak gauge couplings. This calculation has been extended to the
NNLO corrections to the MSSM strange-Yukawa coupling. Our analysis leads to
residual theoretical uncertainties of the effective Yukawa couplings at the
per-cent level.
