The notion of a review article would presume that there exists a coherent body of literature on the topic in question. With agricultural co-operative theory this is not quite the case since it has been approached seriously and systematically in some subject areas but disjointedly if at all in others. This review article attempts to ask what predictions can be made about the behaviour of agricultural co-operatives in the present state of theoretical knowledge—thus, each section refers to a topic that readers might hope to have been investigated in the literature, though the findings are necessarily patchy since few areas have been given adequate attention. Where weaknesses and deficiencies occur, I have tried to point them out and to indicate areas for further research. In doing so, I have hazarded my own ideas, so that much of the material is original. As far as I know, for example, nobody has yet seriously considered the life-cycle of the agricultural co-operative organisation, which constitutes the subject matter of section 7, and the discussion put forward in the first half of section 6, on the supply curve of marketing associations, is also my own work. If these are duplicated in papers which I have failed to bring to light in my quest for material for this article, I can only apologise.