Abstract: Validity is concerned with the clarification and justification of the intended interpretations and uses of observed scores. It has not been easy to formulate a general methodology set of principles for validation, but progress has been made, especially as the field has moved from relatively limited criterion-related models to sophisticate construct models. The watershed event in the development of validity theory has been the development of a well-articulated version of construct validity by L. Cronbach and P. Meehl (1995). The general principles they, and others, have articulated, that validation requires an extended analysis of evidence based on an explicit statement of the proposed interpretation and involving the consideration of competing interpretations, are applicable to all validity arguments.