The present paper completes our earlier results on nonlinear stability of
stationary solutions of the Vlasov-Poisson system in the stellar dynamics case.
By minimizing the energy under a mass-Casimir constraint we construct a large
class of isotropic, spherically symmetric steady states and prove their
nonlinear stability against general, i. e., not necessarily symmetric
perturbations. The class is optimal in a certain sense, in particular, it
includes all polytropes of finite mass with decreasing dependence on the
particle energy.