Following the finding in Chapter 3 that reciprocity encounters limitations when the subjects of a legal relationship are not equal, this chapter analyses the role of reciprocity in rules pertaining to the treatment of individuals in international law, assessing how reciprocity functions differently depending on who rights are owed to in different substantive areas of law. First looking at historical standards of treatment including those based on reciprocity and the use of the minimum standard of treatment, the chapter goes on to examine how reciprocity functions in national treatment and the most-favoured nation clause. The chapter then goes on to examine the treatment of individuals under human rights, international humanitarian law, and international investment law, analyzing the differences that arise in the role of reciprocity when the legal obligations in question are owed directly to individuals. The chapter ends with an examination of recent developments in diplomatic protection.