One model of multithreading gaining popularity on multiprocessor systems is the message-driven model of computation. The message-driven model is a reactive model in which an arriving message starts a block of computation to process that message. The advantage of programming in such a model is that the dependencies are explicit, messages are asynchronous, and the resulting code is highly multithreaded. The message- driven model studied in this paper is the actor model of concurrent computation. This paper presents an empirical performance study of the runtime and kernel support of the ProperCAD II C++ class library which supports the actor model. The ProperCAD II C++ class library facilitates the use of multithread- ing on parallel platforms through object-oriented de- sign techniques. The usefulness of the ProperCAD II is shown through the results of various large, real applications. In addition to providing a useful paradigm to program complex parallel applications, we believe that the actor model integrates well with more advanced performance feedback and visualization tools. Further feedback related to multithreading will be presented in the form of dynamically weighted actor-method call graphs, method specific statistics, and program visualization.