BRST symmetry of field redefinitions

Field redefinitions are considered as a special case of BRST gauge fixings of more general field-enlarging transformations. At the two-loop level an extra local term in the action, the Gervais-Jevicki potential, is generated by point canonical transformations in the bosonic part of the theory. The authors give an example of how this additional term can be cancelled by the inclusion of the ghost fields. This is achieved through an anomalous Jacobian factor from the ghost measure. 24 refs