This chapter examines government support for collective action involving diverse participants who are seeking to achieve various agri-environmental objectives. External help from public agencies or other interested bodies is important when barriers are high; nevertheless the benefits stemming from collective action outweigh the costs. This chapter first analyses collective action with and without government support. Secondly, collective action and policy measures are examined, followed by an analysis of the costeffectiveness of collective action measures. Lastly, the policy implications are set out.