The literature on validity provides much more guidance on how to collect various kinds of validity evidence than it does on which kinds of evidence to collect in specific cases. An argument-based approach to validation redresses the balance by linking the kinds of evidence needed to validate a test-score interpretation to the details of the interpretation. This approach can be summarized in terms of a six-step iterative process; the first three steps constitute the formative stage and the last three steps constitute the summative stage. The interpretation is defined as an interpretive argument leading from test scores to statements and/or actions and is validated by evaluating the plausibility of this argument. The evidence supporting the interpretive argument constitutes an argument for the validity of the corresponding interpretation. The details of this validity argument depend on the specific inferences and assumptions in the interpretive argument, but the process of evaluating the interpretive argument provides a general, argument-based approach to validation. A 40-item list of references and a glossary of selected terms are included. (Author/SLD)