The objective of a SEA is to assess ex ante the potential or probable direct and indirect impacts of policies, plans and programmes on the socio-economic conditions and the natural environment in the expected impact area, and to formulate policies to enhance the net potential positive welfare effect of interventions. In the case of IIRSA, SEAs focus on roads and other types of physical (transport) infrastructure. Such ex ante impact assessments are among the requirements that condition financing by multilateral institutions. Moreover, many countries that participate in IIRSA require by law the making of a SEA or EIAs as part of the decision-making process. As there are no generally accepted standards and rules regarding objectives, content and methodology, SEAs differ widely and several alternative approaches are emerging, ranging from a comprehensive approach, a rapid appraisal to a quick scan. The terms of reference of these assessments are specific for each hub but IIRSA-related SEAs have a number of critical components and dimensions in common.