The deficiencies of the current methods to calculate the efficacy of thermal preservation processes and the theories on which they are based have been known to many researchers in the field for many years. Yet, the literature on the subject has had very little impact, if any at all, on the way in which sterility is calculated in the food industry and probably in other industries as well. The same can be said about the way in which microbial inactivation kinetics is taught at universities in the U.S. and around the world. Conservatism and the widespread belief that microbial mortality really follows the first-order kinetics model are probably the main causes.