This book constitutes the refereed proceedings of the 11th International Conference on Theorem Proving in Higher Order Logics, TPHOLs '98, held in Canberra, Australia, in September/October 1998. The 26 revised full papers presented were carefully reviewed and selected from a total of 52 submissions. Also included are two invited papers. The papers address all current aspects of theorem proving in higher order logics and formal verification and program analysis. Besides the HOL system, the theorem provers Coq, Isabelle, LAMBDA, LEGO, NuPrl, and PVS are discussed.