This volume is a collection of selected papers that were presented at the international conference Model-Based Reasoning in Science and Technology. Abduction, Logic, and Computational Discovery (MBR09 BRAZIL), held at the University of Campinas, Campinas, Brazil in December 2009. A previous volume,Model-Based Reasoning in Scienti?c Discovery,edited by L. Magnani, N.J. Nersessian, and P. Thagard (Kluwer Academic/Plenum Publishers, New York, 1999; Chinese edition, China Science and Techn- ogy Press, Beijing, 2000), was based on the papers presented at the ?rst "model-based reasoning"international conference, held at the University of Pavia, Pavia, Italy in December 1998. Other two volumes were based on the papers presented at the second "model-based reasoning" international c- ference, held at the same place in May 2001: Model-Based Reasoning. Sci- ti?c Discovery, Technological Innovation, Values, edited by L. Magnani and N.J. Nersessian(Kluwer Academic/PlenumPublishers,New York, 2002)and Logical and Computational Aspects of Model-Based Reasoning,editedbyL. Magnani,N.J. Nersessian,and C. Pizzi(KluwerAcademic, Dordrecht,2002). Another volume Model-Based Reasoning in Science and Engineering,edited byL.Magnani(CollegePublications,London,2006),wasbasedonthepapers presentedat the third"model-basedreasoning"internationalconference,held at the same place in December 2004. Finally, volume Model-Based Reasoning inScienceandMedicine,editedbyL.MagnaniandL.Ping(Springer,Heid- berg/Berlin 2006), was based on the papers presented at the fourth"mod- based"reasoning conference, held at Sun Yat-sen University, Guangzhou, P. R. China.