The MoDELS (Model Driven Engineering, Languages, and Systems) conference is a continuation of the successful series of UML conferences. This volume contains the ?nal versions of the technical papers presented at MoDELS 2005 in Montego Bay, Jamaica, October 2-7, 2005. The UML series began in 1988 at Mulhouse, France when the Uni?ed Modeling Language was relatively new. Since then the conferences have been annually, with an increase in both attendance and the breadth of the work presentedattheconferences.Theappearanceofnewresearchareasandtopicsin prior conferences was the motivation for renaming the conference to re?ect the broadermissiontheconferenceswereenabling.Amongthenewareastakingtheir place alongside UML and related standards, such as Model Driven Architecture (MDA), are model refactoring, aspect oriented modeling, and model quality control. The call for papers for MoDELS 2005 resulted in the submission of 215 abstracts and 166 papers. Each submission was reviewed by at least 3 referees assignedfromthesetof51ProgramCommitteemembers.Afterseveralroundsof discussion within the ProgramCommittee, 46 papers (40 scienti?c papers and 6 experience papers) were selected for publication. The Program Committee also selected a paper for the Best Paper MoDELS 2005 Award. The paper is by Friedrich Steimann and is titled "Domain Models are Aspect Free." The review process was managed using the VirtualChair reviewing system, developed by Vahid Garousi at Carleton University, Ottawa, Canada.