  Because of the existence of cubic scalar couplings, there are in general
nondecoupling effects at tree level in the scalar sector of any theory with two
or more very different mass scales. We show this explicitly in the minimal
nonsupersymmetric SU(5) model of grand unification. We show also how tree-level
decoupling is guaranteed if supersymmetry is imposed. On the other hand, if the
gauge symmetry is larger than that of the standard model at the mass scale of
supersymmetry breaking, the two-Higgs-doublet structure at the presumably lower
electroweak energy scale will be different from that of the minimal
supersymmetric standard model, as shown already previuosly in a number od
specific examples. We add here one example involving four Higgs doublets.
