This book constitutes the refereed proceedings of the 18th Workshop on Logic, Language, Information and Communication, WoLLIC 2011, held in Philadelphia, PA, USA, in May 2011. The 21 revised full papers presented were carefully reviewed and selected from 35 submissions. Among the topics covered are various aspects of mathematical logic, computer science logics, philosophical logics, such as complexity theory, model theory, partial order, Hoare logics, hybrid logics, Turing machines, etc.