Implications of the multiple-use of accountability assessments for the process of validation are examined. Multiple-use refers to the simultaneous use of results from a single administration of an assessment for its intended use and for one or more additional uses. A theoretical discussion of the issues for validation which emerge from multiple-use is provided focusing on the increased stakes that result from multiple-use and the need to consider the interactions that may take place between multiple-uses. To further explore this practice, an empirical study of the multiple-use of the Education Quality and Accountability Office Grade 9 Assessment of Mathematics, a mandatory assessment administered in Ontario, Canada, is presented. Drawing on data gathered in an in-depth case study, practices associated with two of the multiple-uses of this assessment are considered and evidence of ways these two uses interact is presented. Given these interactions, the limitations of an argument-based approach to validation for this instance of multiple-use are demonstrated. Some ways that the process of validation might better address the practice of multiple-use are suggested and areas for further investigation of this frequently occurring practice are discussed.