This book constitutes the thoroughly revised post-workshop proceedings of the first annual workshop held under the auspices of the ESPRIT Working Group 21900 TYPES in Aussois, France in December 1996. The 18 revised full papers presented in the book were carefully reviewed and selected from the 30 papers accepted for presentation at the workshop. All current aspects of type theory and type systems and their applications to program verification and theorem proving are addressed; the proof systems and theorem provers dealt with include Coq, LEGO, and Isabelle/HOL.