The role of voluntary and mandatory quality management systems (QMS) is changing in an era of increasing international agri-food trade. This trade environment requires cooperative activity among nations to determine the equivalence of domestic regulatory programs, and thereby facilitate trade. At the same time, voluntary QMS are growing in importance as a means of certifying quality. This paper focuses on two QMS (mandatory HACCP-based programs and the voluntary ISO 9000 certification series) currently applied throughout agri-food supply chains. Their independent and interactive impacts are assessed under this new trade environment.