The 40th ACM Symposium on Theory of Computing (STOC 2008), sponsored by the ACM Special Interest Group on Algorithms and Computation Theory, will be held in Victoria, British Columbia, Saturday, May 17 - Tuesday, May 20, 2008. Typical but not exclusive topics of interest include: algorithms and data structures, computational complexity, cryptography, computational geometry, algorithmic graph theory and combinatorics, randomness in computing, parallel and distributed computation, machine learning, applications of logic, algorithmic algebra and coding theory, computational biology, computational game theory, quantum computing and other alternative models of computation, and theoretical aspects of areas such as databases, information retrieval, and networks. STOC 2008 is sponsored by SIGACT (ACM Special Interest Group on Algorithms and Computation Theory).