This book constitutes the proceedings of the Third International Conference on Conceptual Structures, ICCS '95, held in Santa Cruz, California in August 1995. Conceptual structures are a modern treatment of Peirce's existential graphs, a graphic notation for classical logic with higher order extensions. Besides three invited papers, there are included 21 revised full papers selected from 58 submission. The volume reflects the state-of-the-art in this research area of growing interest. The papers are organized in sections on natural language, applications, programming in conceptual graphs, machine learning and knowledge acquisition, hardware and implementation, graph operations, and ontologies and theory.