The principal design challenge in Automatic Target Recognition (ATR) is signature variability. Target signatures are known to vary significantly as a function of numerous nuisance parameters, such as aspect angle, depression angle, component articulation, etc. There are several methods that have been used to manage nuisance parameters and the resulting signature variability. The focus of this paper is to define the various methods, provide examples, and illustrate the most common methods. A simple example will be used to compare the performance of the sampling, estimation, and integration methods.