Public Interest Litigation (PIL) refers to the practice of lawyers seeking to precipitate social change through court-ordered decrees that reform legal rules, enforce existing laws, and articulate public norms. Sometimes taking advantage of procedures that allow a single lawsuit to resolve a large number of claims, these public law cases can involve the restructuring of important government institutions, including public schools, mental hospitals, welfare agencies, and prisons and that can affect many thousands of individuals. Although PIL originated in the United States, it is now part of the legal landscape of many nations. This note traces the development of PIL in the United States and its spread to other countries. The note reviews experiences that overlap those with those in the U.S. and those that involve experiments not tried or never successfully achieved in the U.S.