This is the 5th edition of the International Conference on Integrated Formal Methods (IFM). Previous IFM conferences were held in York (June 1999), D- stuhl (November 2000), Turku (May 2002) and Canterbury (April 2004). This year's IFM was held in December 2005 on the campus of the Technische Univ- siteit Eindhoven in The Netherlands. This year IFM received 40 submissions, from which 19 high-quality papers wereselectedbytheProgramCommittee.Besidesthese,theproceedingscontain invited contributions by Patrice Godefroid, David Parnas and Doron Peled. It was 10 years ago that Jonathan P. Bowen and Michael G. Hinchey p- lished their famous Ten Commandments of Formal Methods in IEEE Computer 28(4). Their very ?rst commandment - Thou shalt choose an appropriate - tation - touches the heart of the IFM theme: Complex systems have di?erent aspects, and each aspect requires its own appropriate notation. Classical examples of models for various aspects are: state based notations andalgebraicdatatypesfordata,processalgebrasandtemporallogicsforbeh- ior, duration calculus and timed automata for timing aspects, etc. The central question is how the models of di?erent notations relate. Recently, Bowen and Hinchey presented their Ten Commandments Revisited (in: ACM proceedings of the 10th InternationalWorkshop on Formal Methods for Industrial Critical S- tems). Theydistinghuishvariationsin combiningnotations,rangingfromloosely coupled viewpoints to integrated methods. Thelooselycoupledviewpointsarequitepopular(cf.thesuccessofUML)and are easy to adopt in a leightweight process. They could be useful for specifying and analyzing isolated system aspects. However, the main advantage of formal methods - being able to specify and verify the correctness of complete systems -islost.