This volume contains the proceedings of the 23rd International Conference on Application and Theory of Petri Nets. The aim of the Petri net conferences is to createaforumfordiscussingprogressinthe applicationandtheoryofPetrinets. Typically, the conferences have 100-150participants - one third of these coming from industry while the rest are from universities and research institutions. The conferences always take place in the last week of June. The conference and a number of other activities are co-ordinated by a ste- ing committee with the following members: G. Balbo (Italy), J. Billington (A- tralia), G.De Michelis(Italy), S.Haddad(France), K.Jensen(Denmark), S.- magai (Japan), T. Murata (USA), C.A. Petri (Germany; honorary member), W. Reisig (Germany), G. Rozenberg (The Netherlands; chairman), and M. Silva (Spain). Other activities before and during the 2002 conference included tool dem- strations, extensive introductory tutorials, two advanced tutorials on "Work?ow Management: Models, Methods, and Systems" and "Model Checking", and two workshops on "Software Engineering and Formal Methods" and "Formal Me- ods Applied to Defence Systems". The tutorial notes and workshop proceedings are not published in this volume, but copies are available from the organ- ers. The proceedings can be found at http: //www.jrpit.flinders.edu.au/ CRPIT.html. The 2002 conference was organized by the Computer Systems Engineering Centre, School of Electrical and Information Engineering at the University of South Australia, Adelaide, Australia with assistance from the Department of Computer Science, Adelaide University, Adelaide, Australia. We would like to thankthemembersoftheorganizingcommittee(seenextpage)andtheir teams.