This book constitutes the refereed proceedings of the 7th International Conference on Database Theory, ICDT'99, held in Jerusalem, Israel, in January 1999. The 26 revised full papers presented were carefully reviewed and selected from a total of 89 submissions. Also included are one full invited paper, an abstract of an invited talk, and the summary of a tutorial. The papers are organized in topical sections on query languages, logic, performance, concurrency and distribution, constraint databases, index structures, semi-structured data, mediation, computational issues, and views.