The Guiding Principles on business and human rights draw heavily on the concept of ‘due diligence’ to define and elaborate the corporate responsibility to respect human rights. In the Introduction to the Guiding Principles, the responsibility to respect is defined in terms of due diligence: [T]he corporate responsibility to respect human rights...means that business enterprises should act with due diligence to avoid infringing on the rights of others. Guiding Principles 17-21, which discuss the practical steps that business enterprises should take to discharge this responsibility, appear under the heading ‘[h]uman rights due diligence’. The term ‘due diligence’ is familiar to both lawyers and business people; its broad rhetorical appeal may explain why Professor Ruggie invoked the term. However, in this paper, we argue that the Guiding Principles confuse two very different meanings of the term ‘due diligence.’