This chapter introduces the basic principles of network analysis and provides an overview of the main types of questions that can be answered in the field of ecological and social systems studies. Social interactions between actors affect ecosystem dynamics via their role in the circulation of biological resources and of the knowledge associated with their management. The application of network analysis methods to the study of these two main types of mechanisms is illustrated by three case studies whose results have been published and analyzed in the articles by Thomas and Caillon, Labeyrie et al., and Salpeteur et al. These examples highlight the need to associate network analysis with qualitative approaches, which are essential to understand the social rules and norms regulating interactions between individuals, and are also necessary to understand how these interactions fit into the general system of interactions in the studied social systems.