Thisvolumecollectsasetofpapersaccompanyingthelecturesofthe?fthedition of the International School on Formal Methods for the Design of Computer, Communication and Software Systems (SFM). Thisseriesofschoolsaddressestheuseofformalmethodsincomputerscience asaprominentapproachtotherigorousdesignofcomputer,communication and software systems. The main aim of the SFM series is to o?er a good spectrum of current research in foundations as well as applications of formal methods, which can be of help for graduate students and young researchers who intend to approach the ?eld. SFM 2005 (Moby) was devoted to formal methods and tools for the design of mobile systems and mobile communication infrastructures. This volume is organized into four parts related to mobile computing, which cover models and languages, scalability and performance, dynamic power management, and m- dleware support. Each part is composed of two papers. The opening paper by Montanari and Pistore gives an overview of histo- dependent automata, an extension of ordinary automata that overcomes their limitations in dealing with named calculi. In particular, the authors show that history-dependent automata allow for a compact representation of?-calculus processes, which is suitable both for theoretical investigations and for the v- i?cation of models of agents and code mobility. Bettini and De Nicola's - per presents X-Klaim, an experimental programming language speci?cally - signed to develop distributed systems composed of several components intera- ing through multiple distributed tuple spaces and mobile code. Through a series of examples, the authors show that many mobile code programming paradigms can be naturally implemented by means of the considered language, which c- bines explicit localities as ?rst-class data with coordination primitives.