Automata theory is the foundation of computer science. Its applications have spread to almost all areas of computer science and many other disciplines. In addition, there is a growing number of software systems designed to manipulate automata, regular expressions, grammars, and related structures. This volume contains 24 regular papers from the 8th International Conference on Implementation and Application of Automata (CIAA 2003) held in Santa Barbara, CA, USA, in July 2003 covering various topics in the theory, implementation, and application of automata and related structures. It also includes the abstracts of two invited lectures as well as the abstracts of the poster papers displayed during the conference.