In this article we rethink validation within the complex contexts of high-stakes assessment. We begin by considering the utility of existing models for validation and argue that these models tend to overlook some of the complexities inherent to assessment use, including the multiple interpretations of assessment purposes and the potential interaction of assessment uses. We respond to these limitations by proposing an interpretive approach to validation that we call "validation as narrative case description". This approach uses a case-based framework and hermeneutic methodology to construct and analyse validity evidence and suggests narrative as a representational format for communicating validation claims. We illustrate this approach by considering a case study of a secondary mathematics assessment administered in Ontario, Canada. In introducing this approach, we are contributing to the ongoing dialogue on reconceptualising validation as an interpretive process that serves a generative function. (Contains 1 note.)