The International Conference on Computational Intelligence and Security (CIS) is an annualinternationalconference that bringstogether researchers,engineers, developers and practitioners from both academia and industry to share expe- ence and exchange and cross-fertilize ideas on all areas of computational - telligence and information security. The conference serves as a forum for the dissemination of state-of-the-art research and the development, and implem- tationsof systems,technologiesandapplicationsinthese two broad,interrelated ?elds. This year CIS 2005 was co-organized by the IEEE (Hong Kong) Com- tational Intelligence Chapter and Xidian University, and co-sponsored by Hong Kong Baptist University, National Natural Science Foundation of China, Key Laboratory of Computer Networks and Information Security of the Ministry of EducationofChina,andGuangdongUniversityofTechnology. CIS2005received in total 1802 submissions from 41 countries and regions all over the world. All of them were strictly peer reviewed by the Program Committee and experts in the ?eld. Finally, 337 high-quality papers were accepted yielding an acc- tance rate of 18. 7%. Among them, 84 papers are the extended papers and 253 are the regular papers. The conference was greatly enriched by a wide range of topics covering all areas of computational intelligence and information security. Furthermore, tutorials and workshops were held for discussions of the proposed ideas. Such practice is extremely important for the e?ective development of the two ?elds and computer science in general. Wewouldliketothanktheorganizers:theIEEE(HongKong)Computational Intelligence Chapter and Xidian University for their great contributions and - forts in this big event.