ISKE2009 is the fourth in a series of conferences on Intelligent Systems and Knowledge Engineering. The ISKE2009 proceedings covers state-of-the-art research and development in various areas of Intelligent Systems and Knowledge Engineering, particularly of Intelligent Decision Making Systems.Contents:Computational Intelligence and Expert SystemsData Mining and Data AnalysisIntelligent Decision Support SystemsIntelligent Information ProcessingKnowledge Representation and LearningReadership: Graduate students, researchers and academics in computer science, engineering, economics, management and social science.