The author emphasizes the importance of values, principles and guidelines among the “Social Impact Assessment” (SIA) community. The aim is to guide the SIA community on the social parts of environmental impact assessments to bring about a more sustainable and equitable biophysical and human environment. "Social Impact Assessment includes the processes of analysing, monitoring and managing the intended and unintended social consequences, both positive and negative, of planned interventions (policies, programs, plans, projects) and any social change processes invoked by those interventions" (p.5). The fundamental idea of SIA principles is the improvement of the knowledge of how differential distribution of impacts affects different society members. The author argues that the main impact is the one that is experienced by the most vulnerable social groups. This text is the result of the incipient interest for action principles, planning, policies and evaluation of social consequences and an effort to offer a conventional and useful resource for an international context.