The refereed post-proceedings of the International Workshop of the Types Working Group are presented in this volume. The 17 papers address all current issues in formal reasoning and computer programming based on type theory, including languages and computerized tools for reasoning; applications in several domains, such as analysis of programming languages; certified software; formalization of mathematics; and mathematics education.

This volume is published in Honor of Philip Wadler on the occasion of his 60th birthday, and the collection of papers form a Festschrift for him. The contributions are made by some of the many who know Phil and have been influenced by him. The research papers included here represent some of the areas in which Phil has been active, and the editors thank their colleagues for agreeing to contribute to this Festschrift. We attempt to summarize Phil Wadler's scientific achievements. In addition, we describe the personal style and enthusiasm that Phil has brought to the subject.