In high-risk industries such as construction, mining and energy, subcontractors play an increasingly significant role. A typical arrangement is for the site owner to hire a principal contractor who in turn hires multiple subcontractors. This means that multiple subcontractors from multiple companies can be working on the same site at the same time. There is evidence that the use of subcontractors is not only increasing, but that the accident rates for subcontractor employees are higher than those of operator/site owner employees. Existing research on subcontractors, which focuses on the role of the prime contractor in selecting and managing subcontractors, fails to explain why subcontractors continue to experience higher rates of serious injury even where subcontractor management systems are in place. The purpose of this paper is to understand how and why employees of subcontractors’ experience safety differently from employees of principal contractors. The paper does so by extensively reviewing the applicable literature and reporting on a cross-industry focus group study.