This book constitutes the refereed proceedings of the 11th International Conference on Artificial Intelligence: Methodology, Systems, and Applications, AIMSA 2004, held in Varna, Bulgaria in September 2004. The 52 revised full papers presented were carefully reviewed and selected from 176 submissions. The papers are organized in topical sections on ontology engineering, semantic Web services, knowledge representation and processing, machine learning and data mining, natural language processing, soft computing, neural networks, e-learning systems, multiagent systems, pattern recognition, intelligent decision making, and information retrieval.