Communities are diverse internally in their responses to development projects, and differ in their scale and social character. What they seek from Social Impact Assessment (SIA) can be equally diverse, but communities do share an interest in using SIA to maximise the degree of influence they can exert on government and corporate decisions that affect their economic, social and cultural wellbeing. This chapter evaluates the potential of SIA in this regard, using as a framework the 1998 Aarhus Convention on access to information, public participation in decision-making and access to justice in environmental matters. The chapter concludes that SIA’s considerable potential is not generally realised because statutory SIA focuses primarily on seeking approval for projects, not on facilitating community participation. Community controlled SIA and negotiation of binding contracts with developers can help unlock SIA’s potential to allow participation of communities in decisions that affect them.