Résumé : Little is known theoretically, and even less empirically, about the relationship between firm boundaries and the allocation of decision rights within firms. We develop a model in which firms choose which suppliers to integrate and whether to delegate decisions to integrated suppliers. We test the predictions of the model using a novel dataset that combines measures of vertical integration and delegation for a large set of firms from many countries and industries. In line with the model’s predictions, we obtain three main results: (i) integration and delegation co-vary positively; (ii) producers are more likely to integrate suppliers in input sectors with greater productivity variation (as the option value of integration is greater); and (iii) producers are more likely to integrate suppliers of more important inputs and to delegate decisions to them.