This volume contains papers presented at the Third International Conference on Algebraic Methodology and Sofware Technology (AMAST'93), held at the University of Twente, The Netherlands, 21-25 June 1993. The AMAST conferences aim to promote the use of algebraic methodology as a foundation for software technology, and to examine how universal algebra can provide practical mathematical alternatives to the ad hoc methods commonly used in software development. They are only conferences to focus specifically on this important area of research. The resulting volume covers a variety of software development issues, and testifies to the versatility of algebraic methods when used as conceptual tools in the software development process. The papers present original research in a range of areas, and include a distinguished collection of invited papers by leading researchers in the field. The volume also includes descriptions of six software systems which have been developed using algebraic methods, techniques and tools. Among the topics covered in this volume are: - Algebraic metamathematics; - Functional programming; - Category theory in software engineering; - Modular system design; - Real-time system specification; - Testing theory and applications; - Algebraic semantics of concurrency; - Modal logics and reactive systems; - Design and refinement priciples; - Equational and logic programming; - Algebraic specification in software engineering.