This paper develops a conceptual framework for choosing the most cost-effective intervention along the supply chain to improve food safety. This framework identifies both the initial level of on-farm infection and the potential for new infection post farm-gate as key parameters influencing the relative effectiveness of on-farm and abattoir interventions. In addition, the potential for cost economies of scale in implementing interventions at abattoir compared to on-farm is shown to be a further factor determining the relative cost-effectiveness of these interventions. Overall, it is suggested by the analysis in this paper that successful abattoir interventions will typically be more cost-effective than successful on-farm interventions. These findings are consistent with existing case study evidence.