This description of process evaluation techniques used by the Bureau of Mines for studying proposed processing techniques has been prepared to provide those interested in using these studies with an understanding of the methodology. The methods used for preparing both capital and operating cost estimates are described. Each step in preparing the evaluations is described. Types of equipment costs are shown, and factors used in the estimates are defined. Uses of the estimates are suggested, and several examples are included. The accuracy of various types of estimates is discussed, along with an explanation of the reason for selecting the type used in the Bureau's process evaluation studies.