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.