A class of nonlinear control systems is considered whose state evolves
in the neighborhood of a period orbit. Necessary and sufficient condi
tions are given for tracking a family of output reference trajectories
while rejecting a family of disturbances both generated by a Poisson
stable exosystem. A Poincare map approach is adopted to establish thes
e conditions, along a path similar to the one recently proposed in the
literature for a class of nonlinear control systems whose state evolv
es in the neighborhood of an equilibrium point. An illustrative exampl
e is included.