The aim of this document is to produce a state-of-the-art of the academic literature in order to identify theories and concepts available for: a) describing the structure, the dynamics and the functioning of agricultural advisory services; b) understanding how these services are embedded into national Agricultural Knowledge and Innovation Systems (AKIS), and into various agricultural and rural policies across the European Union (EU) countries; c) providing some conceptual elements to support the methodology for an inventory of agricultural advisory services in EU 27 countries (WP3 of the PRO AKIS project), and for the selection of case studies (WP4 of the PRO AKIS project) . Recentreviews of the literature indicate some challenges for the analysis, the implementation and the evaluation of agricultural advisory services (Faure et al. 2012, Birner et al. 2009). These reviews stress the need to switch towards a best fit perspective: "promoting "one-size-fits-all" approaches are inappropriate for agricultural advisory services.[...] What is important is to build capacity among policy-planners, managers and researchers to identify modes of providing and (...) advisory services that "best fit" the specific conditions and development priorities of their countries" (Birner et al 2009). If such debates have a growing importance in the cntexts of South countries, they need to be intensified in Europe through comparative analyses. The report proposes an analysis of agricultural advisory services according to the diversity of i) their methods, ii) their funding principles and iii) their aims, beyond their common characteristics. It is also possible to propose a consistent set of tools for describing these three dimensions. All these issues also open a new research agenda. Some of them will be considered in the realm of the PRO AKIS project (e.g. systematic reviews of available knowledge on the effectiveness of farm advisory services carried out in WP2; case studies on innovation dynamics in different EU countries in WP 4). This document, as well as the project more globally, aims at contributing to the policy debate, emphasizing the need for a more integrated vision of advisory services as instruments of European policies involving agriculture and innovation.