The 23 full papers and 3 system descriptions included in the volume were carefully reviewed and selected from 46 submissions.They present research on all aspects of the mechanization of tableaux-based reasoning and related methods, including theoretical foundations, implementation techniques, systems development and applications. The papers are organized in the following topical sections: tableau calculi, sequent calculi, theorem proving, formalized proofs, non-wellfounded proofs, automated theorem provers, and intuitionistic modal logics.