This letter proposes to use entropy generation as a measure of the relative merit of heat transfer augmentation techniques relative to each other and to the heat exchange apparatus in which they may be incorporated. In this context, heat transfer augmentation techniques are viewed as design changes capable of reducing the irreversible destruction of useful energy (exergy) in heat exchange equipment. The entropy generation rate takes into account simultaneously the heat transfer and fluidd friction changes associated with implementing a heat transfer augmentation technique. Using in-tube roughness as an example, the letter shows what specific operating conditions must be met before the destruction of exergy can be reduced via heat transfer augmentation. © 1980.