To validate an interpretation or use of test scores is to evaluate the plausibility of the claims based on the scores. An argument-based approach to validation suggests that the claims based on the test scores be outlined as an argument that specifies the inferences and supporting assumptions needed to get from test responses to score-based interpretations and uses. Validation then can be thought of as an evaluation of the coherence and completeness of this interpretation/use argument and of the plausibility of its inferences and assumptions. In outlining the argument-based approach to validation, this paper makes eight general points. First, it is the proposed score interpretations and uses that are validated and not the test or the test scores. Second, the validity of a proposed interpretation or use depends on how well the evidence supports the claims being made. Third, more-ambitious claims require more support than less-ambitious claims. Fourth, more-ambitious claims (e.g., construct interpretations) tend to be more useful than less-ambitious claims, but they are also harder to validate. Fifth, interpretations and uses can change over time in response to new needs and new understandings leading to changes in the evidence needed for validation. Sixth, the evaluation of score uses requires an evaluation of the consequences of the proposed uses; negative consequences can render a score use unacceptable. Seventh, the rejection of a score use does not necessarily invalidate a prior, underlying score interpretation. Eighth, the validation of the score interpretation on which a score use is based does not validate the score use. (Contains 1 figure and 1 note.)