This chapter focuses on the extent to which the human resource management (HRM) of non-outsourced employees may itself be outsourced, and the extent to which it varies according to context. It also discusses central question is therefore whether and how organizations from different countries differ in their use of HRM outsourcing. It is also a practically relevant question, particularly to help decision-makers and policy-makers understand how those institutions and cultures enable or constrain outsourcing decisions. The chapter outlines some of the leading conceptual approaches and discussing some known antecedents of (HRM) outsourcing at the activity, firm and industry level. At the activity level, a dominant theory that helps us understand outsourcing choices is transaction cost economics (TCE). In HRM firms may over time have gained experience in and developed internal systems for selection. By contrast, public sector organizations have probably been much more reluctant to outsource their HRM practices.