This report presents the results of a literature review conducted by the Food and Agriculture Organisation of the UN in 2012 on the impact of voluntary standards on smallholders’ ability to participate in markets. The results are based on an analysis of over 100 studies across a range of commodity sectors and countries. Evidence for impacts, however, comes from studies of just three standards: Global GAP, Fairtrade and organic. Moreover, most studies focus on two commodities: coffee and horticulture products. The majority of studies focus on a handful of countries: Mexico, Kenya, Peru, Costa Rica and Uganda. The results of the review can be summarized as: first, equitable and sustainable supply chain linkages, increased access to assets, and support for cooperative development are incentives for complying with standards. Second, both public and private actors have comparative advantages for supporting voluntary standards and are most effective when combined. Finally, governments can provide services which facilitate the inclusion of smallholders in certified value chains. The study concludes by making policy recommendation on how the public sector can mediate the effects of voluntary standards.