Summary: We consider the stability properties of solutions to parameterized nonlinear complementarity problems
where these are vector inequalities. We characterize the local upper Lipschitz continuity of the (possibly set-valued) solution mapping which assigns solutions to each parameter pair . We also characterize when this solution mapping is locally a single-valued Lipschitzian mapping (so solutions exist, are unique, and depend Lipschitz continuously on the parameters). These characterizations are automatically sufficient conditions for the more general (and usual) case where . Finally, we study the differentiability properties of the solution mapping in both the single-valued and set-valued cases, in particular obtaining a new characterization of -differentiability in the single-valued case, along with a formula for the -derivative. Though these results cover a broad range of stability properties, they are all derived from similar fundamental principles of variational analysis.