As increased use of outsourcing by a number of firms within North American has produced significant changes over the last decade in how the human resource function delivers services. In this article, we draw on transaction cost economics, the resource-based view, the HR architecture literature, and institutional theory to examine why these changes have been observed. Following this, we use these same theoretical perspectives to examine how different types of firms are likely to make use of outsourcing in the future to provide human resource services and programmes.