Real-time systems usually involve a subtle interaction of a number of distributed components and have a high degree of parallelism, which makes their performance analysis quite complex. Thus, traditional techniques, such as simulation, or state-based formal methods usually fail to produce reasonable results. The main limitation of these approaches may be overcome by conducting the performance analysis of real-time systems using higher-order-logic theorem proving. This chapter is mainly oriented towards this emerging trend and it provides the details about analyzing both functional and performance related properties of real-time systems using a higher-order-logic theorem prover (HOL). For illustration purposes, the Stop-and-Wait protocol, which is a classical example of real-time systems, has been considered as a case-study.