This paper presents a systematic procedure for selecting optimization variables in a refrigerated gas plant (RGP) using the Taguchi method. A dynamic RGP model developed under HYSYS environment is utilized as a test bed. Nine variables with three levels each are employed for optimizing RGP profit. These optimization variables are selected due to their roles as manipulated variables in controlling the process. Results are validated by comparing optimum values of RGP profit obtained through a set of HYSYS experiments and those from analyses of means. © 2010.