This book constitutes the refereed proceedings of the 18th IFIP TC 6/WG 6.1 International Conference on Testing Communicating Systems, TestCom 2006, held in New York, NY, USA, in May 2006.

The 23 revised full papers presented were carefully reviewed and selected from initially 48 submissions. The papers address all current issues in testing communicating systems, ranging from classical telecommunication issues to general software testing. They were presented in 8 sessions whose scope covered testing theory and foundations; testing non-deterministic and probabilistic systems; testing the Internet and industrial systems; TTCN-3; compositional and distributed testing; FSM-based testing and diagnosis; testing timed systems; and testing for security.