This report sets out key lessons learned from five pilot projects that tested the practical applicability of the principles for effective operational-level grievance mechanisms involving businesses and their stakeholders proposed by the Special Representative of the UN Secretary-General for Business and Human Rights (SRSG), Professor John Ruggie. The pilot project involved the following five companies: Cerrejon Coal (mining sector, Colombia); Esquel Group (apparel sector, supplier factory in Vietnam; Hewlett-Packard (electronics sector, supplier factories in China); Sakhalin II (oil and gas sector, Russia); and Tesco (food sector, producers in South Africa). The report outlines the benefits of developing grievance mechanisms that are aligned with the SRSG’s principles, as well as suggesting how the proposed principles themselves could be further refined to reflect operational realities. These recommendations are reflected in the UN Guiding Principles on Business and Human Rights. This report was developed as part of a project of the Corporate Social Responsibility Initiative at Harvard Kennedy School in support of the SRSG’s mandate.