Invited Papers -- On the Correctness of Operating System Kernels -- Alpha-Structural Recursion and Induction -- Regular Papers -- Shallow Lazy Proofs -- Mechanized Metatheory for the Masses: The PoplMark Challenge -- A Structured Set of Higher-Order Problems -- Formal Modeling of a Slicing Algorithm for Java Event Spaces in PVS -- Proving Equalities in a Commutative Ring Done Right in Coq -- A HOL Theory of Euclidean Space -- A Design Structure for Higher Order Quotients -- Axiomatic Constructor Classes in Isabelle/HOLCF -- Meta Reasoning in ACL2 -- Reasoning About Java Programs with Aliasing and Frame Conditions -- Real Number Calculations and Theorem Proving -- Verifying a Secure Information Flow Analyzer -- Proving Bounds for Real Linear Programs in Isabelle/HOL -- Essential Incompleteness of Arithmetic Verified by Coq -- Verification of BDD Normalization -- Extensionality in the Calculus of Constructions -- A Mechanically Verified, Sound and Complete Theorem Prover for First Order Logic -- A Generic Network on Chip Model -- Formal Verification of a SHA-1 Circuit Core Using ACL2 -- From PSL to LTL: A Formal Validation in HOL -- Proof Pearls -- Proof Pearl: A Formal Proof of Higman’s Lemma in ACL2 -- Proof Pearl: Dijkstra’s Shortest Path Algorithm Verified with ACL2 -- Proof Pearl: Defining Functions over Finite Sets -- Proof Pearl: Using Combinators to Manipulate let-Expressions in Proof.This volume constitutes the proceedings of the 18th International Conference on Theorem Proving in Higher Order Logics (TPHOLs 2005), which was held during22–25August2005inOxford,UK.TPHOLscoversallaspectsoftheorem proving in higher order logics as well as related topics in theorem proving and veri?cation. There were 49 papers submitted to TPHOLs 2005 in the full research c- egory, each of which was refereed by at least three reviewers selected by the programcommittee. Of these submissions, 20 researchpapersand 4 proof pearls were accepted for presentation at the conference and publication in this volume. In keeping with longstanding tradition, TPHOLs 2005 also o?ered a venue for the presentation of work in progress, where researchers invited discussion by means of a brief introductory talk and then discussed their work at a poster session. A supplementary proceedings volume was published as a 2005 technical report of the Oxford University Computing Laboratory. The organizers are grateful to Wolfgang Paul and Andrew Pitts for agreeing to give invited talks at TPHOLs 2005.