This document includes guidelines for conduct of performance monitoring of fossil-fueled steam plants and of the balance-of-plant portion of nuclear power plants. The guidelines include performance monitoring concepts, a description of various methods available, and means for evaluating particular applications. The guidelines provide procedures for validation and interpretation of data, determination of performance characteristics and trends, determination of sources of performance problems, analysis of the performance in relation to the process, determination of losses due to degradation, possible corrective actions, and performance optimization. The guidelines provide the necessary information for implementing a performance monitoring program, using either an automated or a manual data acquisition system.