HEAVY-FERMION EFFECTS IN E+E--]ZH AND Z-]H-UPSILON-UPSILON-BAR-

We consider the effects of the one-loop radiative corrections due to virtual heavy fermions on the process e+e- --> ZH and on the related process Z --> HvvBAR. We show how to compute the one-loop corrections for asymptotically large fermion masses in a very simple manner, using the equivalence theorem where the on-shell Z is replaced by the corresponding Goldstone scalar. Since heavy fermions do not decouple from low-energy phenomena involving the production of external Higgs bosons, the corrections lead to a significant reduction in the rate if there is a heavy fourth generation of quarks and/or leptons.