THE PRESENT DISCUSSION is neither intended as a review of the myriad products and formulations that have over the years been proposed for the inhibition of corrosion processes in a multitude of environments with various substrates, nor a dissertation of the many mechanistic concepts that have been proposed for corrosion inhibition. Rather, an effort shall be made to outline a methodology (or methodologies) narrowly focused on a specific objective: the assessment of the reduction of the rates of corrosion (all manifestations thereof) caused by chemicals added to the environment for specific, well defined, purposes. However, in pursuing a specific methodology neither the nature of the inhibitor, nor the underlying corrosion and corrosion mechanisms can be ignored, and all chemical, physical, and metallurgical realities, as well as their interactions and relationships, must be taken into consideration if the results shall have predictive value.