This volume constitutes the proceedings of the 21st International Colloquium on Automata, Languages and Programming (ICALP 94), held at Jerusalem in July 1994. ICALP is an annual conference sponsored by the European Association on Theoretical Computer Science (EATCS). The proceedings contains 48 refereed papers selected from 154 submissions and 4 invited papers. The papers cover the whole range of theoretical computer science; they are organized in sections on theory of computation, automata and computation models, expressive power, automata and concurrency, pattern matching, data structures, computational complexity, logic and verification, formal languages, term rewriting, algorithms and communications, graph algorithms, randomized complexity, various algorithms.