The performance of a system is a combination of both its correctness and its timeliness. This is of particular concern in systems with dynamic safety conditions such as aircraft, ambulance dispatch systems, and medical monitoring systems. It is of equal concern when the performance of a complex system will mean the difference between it selling and not. The book develops a prioritized probabilistic synchronous process algebra (WSCCS), a modest extension of Milner's SCCS, that is sufficiently rich to capture these kinds of performance problems. The process algebra is defined operational and its algebra derived with respect to a form of probabilistic equality due to Larsen and Skou. Simple exercises of the use of the system to describe performance problems in protocols will be used as an illustration of the syntax and semantics of WSCCS. Other toolsets and industrial-scale examples are provided. An essential resource for computer scientists and software engineers designing, analyzing, and verifying real-time concurrent computer and software systems.