Herein is reviewed the utility of scaling relations and pitfalls to be avoided in their application. This is illustrated by recourse to a discussion of selected proposed scaling relationships including their range of validity, experimental foundation and efficacy in determining the basis of fundamental physical interaction processes. The latter is illustrated using the scaling of damage threshold with the duration of an incident laser pulse. It is shown that for a defect dominated pulsed laser interaction mechanism, the pulse length scaling dependence can change over a narrow range due to a variation of the characteristics of the defect which is most sensitive or easiest to damage under the experimental conditions of import even though the gross aspects of the interaction mechanism do not change appreciably.