The Symposium on Theoretical Aspects of Computer Science is organized jointly by the Special Interest Group for Applied Mathematics of AFCET (Association Française de Cybernétique Economique et Technique) and the Special Interest Group for Theoretical Computer Sciences of GI (Gesellschaft für Informatik). It is held alternately in France and in Germany. This volume contains two invited papers, on combinatorial methods in computer science, and on the complexity of local optimization, and 24 contributions on theoretical aspects of computer science. Some software systems are presented showing the possibilities of applying theoretical research to the realization of software tools.