This book constitutes the refereed proceedings of the 11th International Conference on Logic for Programming, Artificial Intelligence, and Reasoning, LPAR 2004, held in Montevideo, Uruguay in March 2005.

The 33 revised full papers presented together with abstracts of 4 invited papers were carefully reviewed and selected from 77 submissions. The papers address all current issues in logic programming, automated reasoning, and AI logics in particular description logics, fuzzy logic, linear logic, multi-modal logic, proof theory, formal verification, protocol verification, constraint logic programming, programming calculi, theorem proving, etc.