StarLink corn, a variety not approved for human use, disrupted the marketing system in 2000 because of inadvertent commingling. This paper provides an overview of the economics of testing grain for biotech content. What are the risks facing buyers and sellers, and how are these influenced by testing protocols? How do market premiums and discounts, testing costs, and prior beliefs affect the incentives to test? A conceptual model is developed in which sellers choose whether to pre-test grain prior to shipment. Through simulation analysis, we illustrate the impact of market premiums and other variables on testing incentives and buyer risk.