According to international review, discussion, and recent experiences in Thailand, HSRI has concluded that effectiveness of an HIA process depends on the development of four pillars: appropriate analytical frameworks for a continuously participatory learning process have to be demonstrated; an effective institutional structure has to be designed to facilitate HIA implementation and to influence HIA process, impacts, and outcomes in public policy – making; a critical mass of well – understood technical experts and activists needs to be formed to support the satisfactory performance of the other pillars; and an enabling environment must be established for the learning process, fostering constructive dialogue and advocating healthy public policy. The creation of an enabling environment is essential and includes different activities that facilitate public communication on health public policy issues, such as newsletters, websites, broadcasts, and local and international forums.