The goal of this project is to develop a computer simulation model which allows the user to specify the container size, contamination prevalence, agent concentration and agent distribution. The model will be able to address differing sampling requirements for agents able to cause illness at very low doses (e.g., E. coli O157:H7), as well as agents where higher doses are required (e.g., F. tularensis). The simulation will have a user-friendly interface so that it can be used by non-experts to study the influence of different factors. The computer model will include simulated diagnostic tests with user specified false positive and false negative rates, along with a specified sample size and the number of samples to collect. The computer model will be evaluated using a variety of scenarios with specific agents and matrices to determine which variables are more important in the design of tests for agents used in intentional contamination events.