The 12th International Conference on Implementation and Application of - tomata CIAA 2007 washeld at the Czech Technical Universityin Prague,Czech Republic on July 16-18, 2007. These proceedings contain the papers that were presented at CIAA 2007, as well as the abstracts of the poster papers that were displayed during the conference. The proceedings also include the abstracts and extended abstracts offourinvitedlecturespresentedbyGheorghePau ? n,MichaelRiley,MosheVardi, and Bruce W. Watson. The 23 regular papers and 7 poster papers were selected from 79 submitted papers covering various topics in the theory, implementation, and application of automataandrelatedstructures.Eachsubmitted paper wasreviewedbyatleast threeProgramCommitteemembers,with the assistanceofreferees.Theauthors of the papers presented here come from the following countries: Canada, Czech Republic, Denmark, Finland, France, Germany, Greece, Israel, Italy, Poland, Romania, Russia, South Africa, Spain, Sweden, UK, and USA. We wish to thank all those who made this meeting possible: the authors for submitting papers, the Program Committee members and external referees (listed on pages VII and VIII) for their excellent work, and last but not least our four invited speakers. Finally, we wish to express our sincere appreciation to the sponsors and local organizers.