This report sets out key lessons learned from a pilot project conducted in 2009-2010 to test the practical applicability of a set of principles for effective non-judicial grievance mechanisms...involving businesses and their stakeholders. The principles were developed by the [UN] Special Representative [on business & human rights]...The project focused on operational-level grievance mechanisms – that is, mechanisms developed by companies with/for stakeholders affected by their operations. The companies involved in the four main pilots...were Carbones del Cerrejón [joint venture Anglo American, BHP Billiton, Xstrata]...in Colombia; Esquel Group...in Viet Nam; Sakhalin Energy...in the Russian Federation; and Tesco Stores..., working with suppliers in South Africa...Section III reflects cross-cutting lessons learned, setting them out under each principle in turn, and concluding with an explanation of how the principle was adjusted to reflect the learning... [Also refers to HP, Delta Electronics, Chicony Electronics. Annexes with specific lessons from each pilot by Luc Zandvliet, CDA Collaborative Learning; Doug Cahn; Stephan Sonnenberg, Harvard Negotiation and Mediation Clinical Program]