1 COMPLEX SYSTEMS: ANALYSIS AND MODELS OF REAL-WORLD NETWORKS P. CRUCITTI Scuola Superiore di Catania Via S.Paolo 73, 95123, Catania, Italy V. LATORA Dipartimento di Fisica e Astronomia, Università di Catania and INFN sezione di Catania, Italy M. MARCHIORI W3C and Lab. For Computer Science, Massachusetts Institute of Technology, USA and Dipartimento di Informatica, Università di Venezia, Italy A. RAPISARDA Dipartimento di Fisica e Astronomia, Università di Catania and INFN sezione di Catania, Italy Most real-world networks present some similar remarkable properties, as small “shortest path length”, high “clustering”, low “cost” and scale-free degree distribution. In this paper we analyze these properties and quantify them with appropriate variables. Then we compare some well-known models, focusing our attention on how accurate they are in representing real-world networks. 1. Introduction Recently, an always increasing attention is devoted to the study of Complex Systems, i.e. systems composed of a large amount of elementary components that