The structure of polydisperse hard sphere fluids, in the presence of a wall
, is studied by the Rosenfeld density functional theory. Within this approa
ch, the local excess free energy depends on only four combinations of the f
ull set of density fields. The case of continuous polydispersity thereby be
comes tractable. We predict, generically, an oscillatory size segregation c
lose to the wall, and connect this, by a perturbation theory for narrow dis
tributions, with the reversible work for changing the size of one particle
in a monodisperse reference fluid.