STACS,the SymposiumonTheoreticalAspects ofComputerScience,isheld- nually, alternating between France and Germany. STACS is organizedjointly by the Special Interest Group for Theoretical Computer Science of the Gesellschaft f¨ ur Informatik (GI) in Germany and the Maison de l’Informatique et des Ma- ematiquesDiscr etes(MIMD)inFrance.STACS2000wasthe17thintheseries.It was held in Lille from February 17th to 19th, 2000. Previous STACS symposia took place in Paris (1984), Saarbru ¨cken (1985), Orsay (1986), Passau (1987), Bordeaux (1988), Paderborn (1989), Rouen (1990), Hamburg (1991), Cachan (1992),Wu ¨rzburg(1993),Caen(1994),Mu ¨nchen(1995),Grenoble(1996),Lub ¨ eck (1997), Paris (1998), and Trier (1999). All STACS proceedings have been p- lished in the Lecture Notes in Computer Science of Springer-Verlag. STACS has become one of the most important annual meetings in Europe for the theoretical computer science community. It covers a wide range of topics in the area of foundations of computer science. This time, 146 submissions from 30 countries were received, all in electronic form. Jochen Bern designed the electronic submission procedure, which performed marvelously. Many thanks to Jochen.