Protection of New Zealand's native biodiversity and its primary production both depend on biosecurity measures to prevent invasion by alien, or exotic, organisms. At the same time, New Zealand's dependence on trade and travel in an increasingly globalised world places growing strain on the nation's biosecurity systems. Invasion by exotic species has potential for catastrophic impacts on both native biodiversity and human economic and social well-being. New Zealand's biosecurity policies have been gradually evolving from a narrow focus on production pests to a broader awareness of multiple economic, social and ecological objectives. This paper is about the process of reconciling conflicting objectives for biosecurity, with New Zealand as a case study example.