This volume contains papers selected for presentation at the Silver Jubilee 25th Symposium on Mathematical Foundations of Computer Science | MFCS 2000, held in Bratislava, Slovakia, August 28 { September 1, 2000. MFCS 2000 was organized under the auspices of the Minister of Education of the Slovak Republic, Milan Ft a cnik, by the Slovak Society for Computer Science, and the Comenius University in Bratislava, in cooperation with other institu- ons in Slovakia. It was supported by the European Association for Theoretical Computer Science, the European Research Consortium for Informatics and - thematics, and the Slovak Research Consortium for Informatics and Mathe- tics. The series of MFCS symposia, organized alternately in the Czech Republic, Poland, and Slovakia since 1972, has a well-established tradition. The MFCS symposia encourage high-quality research in all branches of theoretical computer science. Their broad scope provides an opportunity of bringing together spec- lists who do not usually meet at specialized conferences. The previous meetings took place in Jablonna, 1972; Strbsk e Pleso, 1973; Jadwisin, 1974; Mari ansk e L azn e, 1975; Gdansk, 1976; Tatransk a Lomnica, 1977; Zakopane, 1978; Olomouc, 1979; Rydzina, 1980; Strbsk e Pleso, 1981; Prague, 1984; Bratislava, 1986; C- lsbad, 1988; Porabk a-Kozubnik, 1989; Bansk a Bystrica, 1990; Kazimierz Dolny, 1991; Prague, 1992; Gdansk, 1993, Ko sice, 1994; Prague, 1995; Krak ow, 1996; Bratislava, 1997; Brno, 1998; and Szklarska Poreba, 1999.