This paper examines economic factors present when setting quarantine zones for contagious livestock diseases like foot-and-mouth disease (FMD). A conceptual model explores the trade-offs as zone size expands. One trade-off is between the cost of economic activity inside the zone and the benefits of reduced disease spread. There are also agricultural and non-agricultural price effects to consider. Two hypothetical counties are constructed to illustrate the ides. Town or city location is critical to the size. Livestock density is inversely related to zone size with low density regions able to reduce disease spread at relatively low cost.