The book, Agricultural Biotechnology: Issues and Choices Information for decision Makers, from USDA and Land Grant Colleges discusses risk evaluation for the use of legislators concerned with public policy. However, that discussion is entirely theoretical. The 1970 epidemic of Southern Corn Leaf Blight caused by the pleiotropic gene for Cytoplasmic Male Sterility provides material to use in real-world risk evaluation for biotechnology. Approximately 1×1012 corn seeds are planted annually in the US. Assuming a mutation rate of 1×10-6, then 1×106 mutations can be expected annually. The poster will evaluate the importance of this number using assumptions based on fold-increase during seed production. Unfortunately, it is not possible to evaluate the risk of incorporating another pleiotropic gene into commercial crops because insufficient data are available on the frequency of pleiotropy.