An increasing volume of literature deals with different meanings of the term 'extension' due to the many different agricultural extension systems (AESs) in use. Acknowledging the diversity of AESs, the authors recognize that there is usually a bias towards some specific aspect of these interventions that indicates a need to consider a systemic framework for comparative studies. The main purpose of this contribution is therefore to identify such a systemic view, which could be applied to comparative studies of AESs. Three levels of analysis should be scrutinized for considering a systemic view: micro (institutional), meso (national) and macro (international). At the most basic level, all AESs are involved in both intra-actions and interactions of the extension institution. For this reason, the aim Of many studies has been to evaluate the institutional functions of extension practices. The functions at this lowest level are used to predict not only how extension professionals think and act, but how they react to their different target groups. The main question at the micro level is therefore to understand how a country can reach its agri-rural development goals through extension institutions and what institutional arrangements and funding trends help to achieve those goals. At the meso level, the most important considerations are national expectations, which lead to governmental support for or restrictions oil the extension institution. Socioeconomic conditions and their consequences largely determine what the extension tasks should be. The main question at this level is why a country needs extension services, which define the different missions for them in different countries. Finally, at the macro level of analysis, it is important first to consider international components and their impact on the level of socioeconomic development of particular countries and, then, the extension missions. The main issue at this level is therefore to understand what international forces and considerations affect the present situation of a country and hence create new expectations of the extension system.
