This book constitutes the refereed proceedings of the 7th International Conference on Discovery Science, DS 2004, held in Padova, Italy in October 2004.The 20 revised long papers and the 19 revised regular papers presented were carefully reviewed and selected from 80 submissions. The papers are organized in topical sections on pattern mining, classification, outlier detection, clustering, feature construction and generation, knowledge acquisition, discovery science in reality, machine learning algorithms, Web mining, applications of predictive methods, and interdisciplinary approaches.