This book constitutes the refereed proceedings of the 4th International Conference on Logical Aspects of Computational Linguistics, LACL 2001, held in Le Croisic, France, in June 2001. The 16 revised full papers presented together with two invited papers were carefully reviewed and selected for presentation. Among the topics covered are categorical grammars, dependency grammars, formal language theory, grammatical inference, hyperintensional semantics, minimalism, type-logical semantics, language learning, and natural language processing.