  Based on quantitative ``{\sc kam} theory'', we state and prove two theorems
about the continuation of maximal and whiskered quasi--periodic motions to
slightly perturbed systems exhibiting proper degeneracy. Next, we apply such
results to prove that, in the three--body problem, there is a small set in
phase space where it is possible to detect both such families of tori. We also
estimate the density of such motions in proper ambient spaces.
  Up to our knowledge, this is the first proof of co--existence of stable and
whiskered tori in a physical system.
