This thesis examines how two of New Zealand's largest primary producer industries negotiated their relationship with the highly controversial practice of genetic modification. This was in an effort to maintain their dominance in export markets, at a time when genetically modified foods were on the one hand regarded as a possible liability in the marketplace, and on the other hand offered the apparent potential for innovation and economic gain. The two case studies featured in this thesis-the dairy industry and the kiwifruit industry-both earn significant export incomes and are seen as national icons as well as major institutions for New Zealand. However, these two industries take differing positions in the debate about genetic modification. The kiwifruit industry has urged extreme caution while the dairy industry has argued for rapid involvement in genetic modification. The research takes a critical-interpretive perspective on the two cases. The study is both issue- and case-driven, and uses a combination of rhetorical criticism and discourse analysis to examine the social construction of meanings about genetic modification. The research focus is on the intersection of public relations and organisational communication, including issues management, and especially on the ways in which rhetoric is used as a means of managing multiple organisational identities. The research findings indicate that the positioning of these two industries on genetic modification is largely market-driven. The differences in their policies result from contrasting industry products, industry markets, and industry cultures. The values and values-related tensions, expressed explicitly and implicitly in the research data, indicate that there is a dynamic interplay between the rationalities used by the industries to justify their positioning on genetic modification and the multiple identities that need to be managed by each industry. In the kiwifruit industry, environmental concerns are highlighted by an emphasis on 'soft' pest management and organic production, and kiwifruit become a luxury raw product sold mainly to markets in Europe and Japan. In the dairy industry, commodity milk products compete on the basis of low-cost, efficient production, and the major markets are in South East Asia and Latin America. This thesis contributes to recent work on corporate identity and organisational communication. Significantly, it demonstrates how the blurring of boundaries between internal and external organisational communication has increased the need for a more complex understanding of how organisations manage multiple organisational identities, particularly where broader socio-political issues, including national identities and international markets, are concerned.