Economic threshold, also called optimizing threshold, has been defined by economists to be the level of pest infestation that warrants an application of pesticide when the pesticide application rate is computed to maximize the grower’s profit. As often used in practice, however, economic threshold is assumed to be the level of pest infestation at which cost of the pest application (when the application rate is a fixed, predetermined value) equals cost of the damage prevented by the application. This is sometimes called the discrete-choice threshold. In either case, computations are ordinarily done assuming that all parameters of the problem are known with certainty. In reality, this assumption is often not correct; there is a great deal of uncertainty. Effect of uncertainty on the economic threshold computation was explored. Uncertainty may have a profound effect as illustrated by consideration of a simple model. Extension of this method to more complex, realistic models is described.