The Montreal Protocol is generally recognized as one of the most successful multilateral environmental agreements - in the sense of achieving its objectives - yet negotiated. The Protocol owes its success to many factors, some of which are not necessarily repeatable in the context of future multilateral environmental agreements (MEAs). The progress of the negotiations in many ways provides a model for international treaty negotiation, fully involving participants from key groups such as business, scientists and non-governmental organizations (NGOs). The experience of the Montreal Protocol suggests that future MEAs dealing with the control of substances causing transboundary environmental damage may find it necessary to incorporate trade provisions. The objectives of trade liberalization and environmental sustainability are not mutually incompatible. The international community, however, does need to devise effective systems for ensuring that the pursuit of one does not prevent the achievement of the other.