This book constitutes the refereed proceedings of the 15th International Conference on Computer Aided Verification, CAV 2003, held in Boulder, CO, USA in July 2003. The 32 revised full papers and 9 tool papers presented were carefully reviewed and selected from a total of 102 submissions. The papers are organized in topical sections on bounded model checking; symbolic model checking; games, trees, and counters; tools; abstraction; dense time; infinite state systems; applications; theorem proving; automata-based verification; invariants; and explicit model checking.