This volume constitutes the refereed proceedings of the Fourth International Conference on Conceptual Structures, ICCS '96, held in Sydney, Australia, in August 1996.The book presents five full papers by the invited speakers together with 15 revised full papers selected for presentation at the conference from a respectable number of submissions. The issues addressed are natural language processing, information retrieval, graph operations, conceptual graph and Peirce theory, knowledge acquisition, theorem proving and CG programming, and order-based organisation and encoding.