Higgs Physics and the Equivalence Theorem

The equivalence theorem is an extremely useful tool to calculate heavy Higgs {\it and} top-quark effects for processes that have center-of-mass-energies (much) larger than the $W$ boson mass. After an explanation of the renormalization procedures involved, the results for one- and two-loop radiative corrections to the fermionic Higgs decay, $H\to f\bar{f}$, are given and discussed. Finally, the renormalization scheme dependence is examined, and the reliability of the perturbative series is investigated.