This book constitutes the thoroughly refereed post-conference proceedings of the 4th International Workshop on Agents and Data Mining Interaction, ADMI 2009, held in Budapest, Hungary in May 10-15, 2009 as an associated event of AAMAS 2009, the 8th International Joint Conference on Autonomous Agents and Multiagent Systems. The 12 revised papers and 2 invited talks presented were carefully reviewed and selected from numerous submissions. Organized in topical sections on agent-driven data mining, data mining driven agents, and agent mining applications, the papers show the exploiting of agent-driven data mining and the resolving of critical data mining problems in theory and practice; how to improve data mining-driven agents, and how data mining can strengthen agent intelligence in research and practical applications. Subjects that are also addressed are exploring the integration of agents and data mining towards a super-intelligent information processing and systems, and identifying challenges and directions for future research on the synergy between agents and data mining.