This volume contains the proceedings of the 17th IFIP TC6/WG6. 1 Inter- tional Conference on Testing of Communicating Systems (TestCom 2005). The conference was held at Concordia University, Montr eal, Canada, from May 31 to June 2, 2005. TestCom 2005 was organized by Concordia University and was sponsored by IFIP. Following the trends initiated at the 16th edition of the conference held in Oxford, UK, the ?rst call for papers issued in summer 2004 called for contri- tions from the general software testing community. The goal of the conference thisyearwas tocontinue the...