The four volume set LNAI 3681, LNAI 3682, LNAI 3683, and LNAI 3684 constitute the refereed proceedings of the 9th International Conference on Knowledge-Based Intelligent Information and Engineering Systems, KES 2005, held in Melbourne, Australia in September 2005.

The 716 revised papers presented were carefully reviewed and selected from nearly 1400 submissions. The papers present a wealth of original research results from the field of intelligent information processing in the broadest sense; topics covered in the first volume are intelligent design support systems, data engineering, knowledge engineering and ontologies, knowledge discovery and data mining, advanced network application, approaches and methods of security engineering, chance discovery, information hiding and multimedia signal processing, soft computing techniques and their applications, intelligent agent technology and applications, smart systems, knowledge - based interface systems, intelligent information processing for remote sensing, intelligent human computer  interaction systems, experience management and knowledge management, network (security) real-time and fault tolerant systems, advanced network application and real-time systems, and intelligent watermarking algorithms.