This book constitutes the refereed proceedings of the 16th Annual Symposium on Theoretical Aspects of Computer Science, STACS 99, held in Trier, Germany in March 1999. The 51 revised full papers presented were selected from a total of 146 submissions. Also included are three invited papers. The volume is divided in topical sections on complexity, parallel algorithms, computational geometry, algorithms and data structures, automata and formal languages, verification, algorithmic learning, and logic in computer science.