Although many governments have privatized their agricultural extension services, there is widespread agreement that the public sector still needs to play a role in the ¿agricultural knowledge market¿ in order to prevent market failure and other undesirable phenomena. However, appropriate mechanisms for intervention in the agricultural knowledge market are still in their infancy. This article discusses the case of the Nutrient Management Support Service (NMSS), a government-funded support service in The Netherlands designed to optimize the fit between the demand and supply of ¿agricultural knowledge products¿ that reduce nutrient emissions into the environment. The activities of the support service were four-fold: (1) distributing vouchers to farmers, (2) establishing mechanisms for quality control, (3) facilitating the articulation of end-users¿ needs, and (4) improving market transparency. We analyze the extent to which the NMSS has succeeded in supporting a demand-driven knowledge market for nutrient management issues. We question some of the conceptual and practical assumptions underlying this style of intervention. In addition, we argue that the notion of demand requires considerable refinement before it can be useful for guiding state involvement in demand-driven extension.