Group affiliation plays a key role in shaping individual opinions on public policy issues. Understanding group-related differences may be important for global organizations that depend on broad public acceptance of their policies. Research indicates that people's opinions become polarized to match perceived opinions of their group and that media reports may signal normative opinions group members should adopt. Surveys administered before and after the World Trad Organization's (WTO) 1999 meeting in Seattle indicated significant differences in opinion by group affiliation. Respondents overall held negative views of the WTO before the meeting, and more negative views after the meeting. Business and civic group members were more positive toward the WTO than were human rights and environmental and union group members, reflecting their self-interests. However, contrary to public opinion theory betweeen-group differences in opinion in many cases became less polarized, whereas attention to media coverage served to further polarize only the opinions of union group members.