Numerous case studies have demonstrated that markets are significantly less integrated and operate more imperfectly in the developing than in the developed world. The prominence of transactions costs resulting from the uneven endowment of actors (particularly of land), asymmetrical information and a whole constellation of institutional and structural constraints leads to a variety of exchange channels and transactions. An approach is developed in this paper that highlights the importance of key elements (characteristic of actors, of the item exchanged and of the physical, technological, cultural and polkcy environment, respectively) in shaping distinct exchange configurations and corresponding transactions. In Section II it is shown how specific characteristics of elements influence the prevailing exchange channels and transactions in agricultural commodity systems. Three types of foodgrains' market segmentation are identified, i.e. parallel, spatial and dual and related to the specific elements (such as government intervention and poor infrastructure) that give rise to them. A comparative evaluation is undertaken of the degree of market integration prevailing in Africa vs. Asia and of the elements giving rise to different types of exchange configurations. Section III focusses on the Pakistan wheat market chain and its decomposition into distinct configurations and transactions. The performance of the whole commodity system and of the configurations constituting it, is evaluated on the basis of efficiency and equity criteria.