The guardian map theory of generalized stability of parametrized linear time-invariant systems is used to prove new results on stability/performance of linear time-invariant singularly perturbed systems with Bn exogenous parameter, i.e. systems that contain, in addition to a singular parameter epsilon, another uncertain parameter mu. The results give necessary and sufficient conditions for generalized stability for all sufficiently small values of epsilon and all values of mu in a given interval [mu(1), mu(2)]. In addition, explicit expressions for the largest upper bound epsilon* on epsilon for guaranteed stability and performance are given and the cases leading to finite or infinite epsilon* are clearly delineated. Thus the results represent a significant addition to the classical Klimushev-Krasovskii theorem, while at the same time providing closed-form expressions for the maximum parameter range for stability and performance.