This chapter looks at the prospects for effective regional action to protect the NW Pacific from environmental harm. Regional environmental governance works best when it is multilateral. The chapter reviews the lessons and experience over the last 25 years from collective efforts at regional marine environmental governance from United Nations Environment Program's (UNEP's) Regional Seas Program. International experience with regional marine governance suggests that five factors are key in constructing regional environmental regimes: national leadership, international institutions, transnational scientific networks, NGOs, and public concern. The most effective regimes have been those with strong international institutions working in conjunction with transnational scientific networks, known as epistemic communities. The primary functions performed by international institutions that improve regional marine governance have been improving the contractual environmental, enhancing national capacity for addressing environmental threat, and building national concern. Each of these functions is addressed in the chapter.