Abstract. We propose an approach to automatic verification of realtime systems against scenario-based requirements. A real-time system is modeled as a network of Timed Automata (TA), and a scenario-based requirement is specified as a Live Sequence Chart (LSC). We define a trace-based semantics for a kernel subset of the LSC language. By equivalently translating an LSC chart into an observer TA and then nonintrusively composing this observer with the original system model, the problem of verifying a real-time system against a scenario-based requirement reduces to a classical real-time model checking problem. We show how this is accomplished in the context of the Uppaal model checker.