This paper addresses a puzzling problem: why do parties often choose to combine alternative modes of organizations simultaneously while dealing with identical or almost identical transactions? I propose a model to capture these so-called ‘plural forms’ and to explain the choice of such non-standard arrangements. Three determinants are identified as playing the major role: ambiguity surrounding the fitness of a mode of organization to the transaction at stake; complexity of a transaction or a set of transactions; and strategic behavior. Propositions are derived that are confronted to empirical data coming out of the agro-food industry. Copyright © 2012 John Wiley & Sons, Ltd.