Fan, Michael K-H.Tits, A.L.The structured singular value (SSV or ) is know to be an effective tool for assessing robust performance of linear time- invariant models subject to structured uncertainty. Yet all a single analysis provides is a bound ݠon the uncertainty under which stability as well as Hperformance level of k/ݠare guaranteed, where k is preselectable. In this paper, we introduce a related quantity, denoted by v which provides answers for the following questions: (i) given ݬ determine the smallest with the peoperty that, for any uncertainty bounded by ݬ an H performance level ofen-UScomputer aided designlinear systemsoptimizationrobust controlstabilityIntelligent ServomechanismsA Measure of Worst-Case HPerformance and of Largest Acceptable UncertaintyTechnical Report