This book constitutes the refereed proceedings of the 4th International Conference on Data Warehousing and Knowledge Discovery, DaWaK 2002, held in Aix-en-Provence, France, in September 2002. The 32 revised full papers presented were carefully reviewed and selected from more than 100 submissions. The papers are organized in topical sections on association rules, clustering, web mining and security, data mining techniques, data cleansing, applications, data warehouse design, OLAP, and data warehouse maintenance.