  We present the currently most accurate prediction of Z pole observables such
as sin^2 theta_eff, Gamma_Z, R_b, R_l, and sigma^0_had in the Minimal
Supersymmetric Standard Model (MSSM). We take into account the complete
one-loop results including the full complex phase dependence, all available
MSSM two-loop corrections as well as the full SM results. We furthermore
include higher-order corrections in the MSSM Higgs boson sector, entering via
virtual Higgs boson contributions. For Gamma(Z -> neutralino{1} neutralino{1})
we present a full one-loop calculation. We analyse the impact of the different
sectors of the MSSM with particular emphasis on the effects of the complex
phases. The predictions for the Z boson observables and M_W are compared with
the current experimental values. Furthermore we provide an estimate of the
remaining higher-order uncertainties in the prediction of sin^2 theta_eff.
