At all levels of abstraction, modern computing systems are built in terms of components and communication (or, at least, synchronisation) between components. Communicating systems imply concurrency, which remains the continuing theme of this WoTUG series. Traditionally, concurrency has been taught and considered and experienced as an advanced and difficult topic. The thesis underlying this conference is that that tradition is wrong. The natural world operates through the continuous interaction of massive numbers of autonomous agents at all levels of granulartiy (sub-atomic, human, astronomic). If modern computer science finds this hard to grasp, then perhaps it is not doing it right! It is time for concurrency to mature into a core engineering discipline that can be used on an everyday basis to simplify problem solutions, as well as to enable them. Communicating Process Architectures 2000 addresses these issues head on. The goal is to stimulate discussion and ideas as to the role concurrency will play in future generations of scaleable computer infrastructure and applications – where scaling means the ability to ramp up functionality (i.e. stay in control as complexity increases) as well as physical metrics (such as performance).