``Augmentation ideals of equivariant cohomology rings.'' J.P.C.Greenlees School of Mathematics and Statistics, Hicks Building, Sheffield S3 7RH. UK. The purpose of this note is to establish a number of useful results about the augmentation ideal $J$ for the coefficient ring $F_G^*$ of a Noetherian complex orientable equivariant cohomology theory. The results show that various naturally occurring substitutes for the ideal have the same radical, and can therefore be used instead of the augmentation ideal in all geometric constructions.