A large number of agricultural development initiatives now support value chain approaches. They encompass most stages of the chain, from inputs supply to production, processing, marketing, and ﬁnancing. Given the complexity of integrated programs, scaling up value chains poses challenges. Chains operate with a multiplicity of actors and require numerous interfaces between the public and private sectors, which often have different objectives and respond to different incentive systems. A particular challenge is to ensure that scaled-up chains will beneﬁt the poor, since chains typically favor better-off farmers, processors, and traders, while poorer actors in the chain, especially smallhold farmers, can get squeezed out. There are two concepts of scaling up in a chain: (i) the development of an integrated chain is in itself a functional scaling up, as primary products are “scaled up” to higher-value-added goods and taken to market, and (ii) value chains are taken to larger scale by increasing the amount of goods produced, processed, and sold. Both scaling up processes rely on drivers and need to overcome numerous constraints on the scaling-up pathway. Common impediments to scaling up are a lack of infrastructure, access to ﬁnancing, access to markets, knowledge of appropriate technology, and the inability to deliver products at sufﬁcient quantity and quality.