  We use the embedding tensor method to construct the most general maximal
gauged/massive supergravity in d=9 dimensions and to determine its extended
field content. Only the 8 independent deformation parameters (embedding tensor
components, mass parameters etc.) identified by Bergshoeff \textit{et al.} (an
SL(2,R) triplet, two doublets and a singlet can be consistently introduced in
the theory, but their simultaneous use is subject to a number of quadratic
constraints. These constraints have to be kept and enforced because they cannot
be used to solve some deformation parameters in terms of the rest. The
deformation parameters are associated to the possible 8-forms of the theory,
and the constraints are associated to the 9-forms, all of them transforming in
the conjugate representations. We also give the field strengths and the gauge
and supersymmetry transformations for the electric fields in the most general
case. We compare these results with the predictions of the E11 approach,
finding that the latter predicts one additional doublet of 9-forms, analogously
to what happens in N=2, d=4,5,6 theories.
