We present an approach for adaptive scheduling of soft realtime legacy applications (for which no timing information is exposed to the system). Our strategy is based on the combination of two techniques: 1) a real-time monitor that observes the sequence of events generated by the application to infer its activation period, 2) a feedback mechanism that adapts the scheduling parameters to ensure a timely execution of the application. By a thorough experimental evaluation of an implementation of our approach, we show its performance and its efficiency. Categories and Subject Descriptors D4.1 [Operating Systems]: Process Management—Scheduling General Terms Experimentation, Performance, Measurement