The theoretical soundness and practical relevance of strategic human resource management (SHRM) scholarship has recently come under scrutiny. The goal of this symposium is to offer a starting point for SHRM scholars to rethink our approach to understanding the achievement of competitive advantage through HR, guided by a reconsideration of what it means to achieve horizontal fit and vertical fit in HRM. Collectively, the three papers in this symposium contribute to this effort through a reconsideration of the content of the HR systems we study, an expansion of the strategic bases against which we consider the vertical fit of HR systems, and a more explicit incorporation of complexity and change into our understanding of both the horizontal and vertical fit of the HR "ecosystems" in organizations. In this paper, I introduce the key issues and questions with which the papers in the symposium interface and highlight potential avenues that future SHRM scholarship could pursue to address them.