Effective lagrangians can be used to parametrize the effects of physic
s beyond the Standard Model. Assuming the complete theory is a gauge t
heory, we determine which effective operators may be generated at tree
level, and which are only generated at loop level. The latter are sup
pressed by factors of 1/16 pi(2) and will therefore be quite difficult
to detect. In particular, all operators changing the Standard-Model s
tructure of the triple-gauge-vector couplings fall into this category.
We also point out that in certain cases, dimension-eight operators ma
y be more important than dimension-six operators. We discuss both the
linear and non-linear representation of the Higgs sector.