Robust stability analysis of a class of synchronized systems is addressed in this work. The problem is focused departing from the μ-analysis of the H ~ control theory. Main question is, if two chaotic systems behave in synchronous way, how stable is the synchronized behavior? A quantitative measure of the robustness margin of the chaotic synchronization is studied in this work. The class of synchronized systems comprises second-order driven oscillators. An illustrative example shows the results of the robustness issues on the chaotic synchronization.