This volume contains the research papers presented at the International C- ference on Automated Reasoning with Analytic Tableaux and Related Methods (TABLEAUX 2009) held July 6-10, 2009 in Oslo, Norway. This conference was the 18th in a series of international meetings since 1992 (listed on page IX). It was collocated with FTP 2009, the Workshop on First-Order Theorem Proving. The Program Committee of TABLEAUX 2009 received 44 submissions from 24 countries. Each paper was reviewed by at least three referees, after which the reviews were sent to the authors for comment in a rebuttal phase. After a ?nal intensive discussion on the borderline papers during the online meeting of the Program Committee, 21 research papers and 1 system description were accepted based on originality, technical soundness, presentation, and relevance. Additionally, three positionpaperswereaccepted, whicharepublished asate- nical report of the University of Oslo. We wish to sincerely thank all the authors who submitted their work for consideration. And we would like to thank the Program Committee members and other referees for their great e?ort and p- fessional work in the review and selection process. Their names are listed on the following page