This book constitutes the refereed proceedings of the 24th International Colloquium on Automata, Languages and Programming, ICALP '97, held in Bologna, Italy, in July 1997. ICALP '97 celebrated the 25th anniversary of the European Association for Theoretical Computer Science (EATCS), which has sponsored the ICALP meetings since 1972. The volume presents 73 revised full papers selected from a total of 197 submissions. Also included are six invited contributions. ICALP is one of the few flagship conferences in the area. The book addresses all current topics in theoretical computer science.