The aim of this document is to produce a state-of-t he-art of the academic literature in order to identify theories and concepts available for: a) de scribing the structure, the dynamics and the functioning of agricultural advisory services; b) understanding how these services are embedded into national Agricultural Knowledge and Innovation Syst ems (AKIS), and into various agricultural and rural policies across the European Union (EU) count ries; c) providing some conceptual elements to support the methodology for an inventory of agricul tural 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) . Recent reviews of the literature indicate some challenges for...