  The masses of the neutral CP-even Higgs bosons in the Minimal Supersymmetric
Standard Model (MSSM) are predicted on the basis of explicit
Feynman-diagrammatic calculations. The results, containing the complete
diagrammatic one-loop corrections, the leading two-loop corrections of O(alpha
alpha_s) and further improvements taking into account leading electroweak
two-loop and higher-order QCD contributions, are discussed and compared with
results obtained by renormalization group calculations. Good agreement is found
in the case of vanishing mixing in the scalar top sector, while sizable
deviations occur if scalar top mixing is taken into account. By means of a
Taylor expansion a compact approximation formula for the mass of the lightest
Higgs boson, m_h, is derived. The quality of the approximation in comparison
with the full result is analyzed.
