The 21st International Conference on Industrial, Engineering and Other Applications of Applied Intelligent Systems (IEA-AIE 2008) held in Wroclaw, Poland was an international scientific forum for researchers in the field of applied artificial intelligence. The presentations of the invited speakers and the authors focused on developing and employing methods and systems to solve real-life problems in all applied intelligence areas. The IEA-AIE conference series, chaired by Moonis Ali, has a very long tradition, and it is the first time it was hosted in Poland. We received 302 papers from 52 countries. Each paper was sent to at least three Program Committee members for review. Although the general quality of the submissions was very high, only 90 best papers were selected for oral presentation and publication in the LNAI proceedings. The papers in the proceedings cover the following topics: computer vision, fuzzy system applications, robot, manufacturing, data mining and knowledge discovery, neural network, machine learning, natural language processing, Internet application, e-learning, heuristic search, application systems, agent-based system, evolutionary and genetic algorithms, knowledge management, and other applications. These papers highlight new trends and frontiers of applied artificial intelligence and show how new research could lead to new and innovative applications. We hope you will find these works useful and inspiring for your own research. We would like to express our sincere thanks to the Program Committee members and all the reviewers for their hard work, which helped us to select the highest quality papers for the conference.