Over the past 20 years, there has been a considerable expansion in theory and research about human resource management and performance. This paper reviews progress by identifying a series of phases in the development of relevant theory and research. It then sets out a number of challenges for the future on issues of theory, management processes and research methodology. The main conclusion from the review is that after over two decades of extensive research, we are still unable to answer core questions about the relationship between human resource management and performance. This is largely attributed to the limited amount of research that is longitudinal and has been able to address the linkages between HRM and performance and to study the management of HR implementation.