  We consider the possibility of an alternative gravity theory explaining the
dynamics of galactic systems without dark matter. From very general assumptions
about the structure of a relativistic gravity theory we derive a general
expression for the metric to order $(v/c)^2$. This allows us to compare the
predictions of the theory with various experimental data: the Newtonian limit,
light deflection and retardation, rotation of galaxies and gravitational
lensing. Our general conclusion is that the possibility for any gravity theory
to explain the behaviour of galaxies without dark matter is rather improbable.
