The emergence of new paradigms for data management raises a variety of exciting challenges. An important goal of database theory is to answer these challenges by providing sound foundations for the development of the field. This volume contains the papers selected for the third International Conference on Database Theory, ICDT'90. The conferences in this series are held biannually in beautiful European cities, Rome in 1986 and Bruges in 1988 with proceedings published as volumes 234 and 326 in the same series. ICDT'90 was organized in Paris by the Institut National de Recherche en Informatique et Automatique. The conference features 2 invited presentations and 31 papers selected from 129 submissions. The papers describe original ideas and new results on the foundations of databases, knowledge bases, object-oriented databases, relational theory, transaction management, data structures and deductive databases. The volume offers a good overview of the state of the art and the current trends in database theory. It should be a valuable source of information for researchers interested in the field.