The "concept of the co-operative identity" (consisting from the definition, aims and functions of cooperatives and the so-termed co-operative principles) serves as a general theoretical background for the economic analysis of agricultural co-operation. The development of Dutch dairy co-operatives is used as a case study example, which suitably illustrates and represents the processes taking place in the European Union. Some suggestions for further research on the co-operative identity according to each country and different branches and sectors in order to see the substance of co-operation from different economic and non-economic aspects are proposed.