This publication contains papers from the Communicating Process Architectures 2006 conference, held at Napier University in Edinburgh. It is perhaps appropriate that a meeting concerning simple ways of designing, implementing and reasoning about concurrent systems should be held in an institution named after the inventor of a simple, and highly concurrent, adding machine. The house in which John Napier lived forms part of the campus where the meeting was held. The papers are very varied and wide ranging and subjects include various aspects of communicating process theory and their application to designing and building systems. One of the hottest current topics - safe and effective programming models for multicore processors (e.g. IBM's Cell) - has a natural home in this community and is addressed. Other papers include a case study on large scale formal development and verification, CSP mechanisms for Microsoft's .NET framework, parallel systems on embedded and mobile devices, modern link technology ('SpaceWire'), various applications of occam, JCSP and JCSP.net (video processing, robotics, massive multiplayer gaming, material and biological modeling, etc.), visual design languages and tools for CSP and real-time systems, new process oriented programming and design environments, new developments of the Transterpreter, efficient cluster computing and the debugging of message-passing systems.