This Article offers a global assessment of the record and promise of international environmental law to the beginning of the millennium. I first present several overall accounts of the contribution of international environmental law. Herein I describe the complexities of undertaking global evaluations. After summarizing the negative and positive evaluations, the Article takes a closer look at five case studies. I then lay out a description of a set of characteristics linked to effective law. Thereafter I look forward, reviewing conditions that are expected in the policy world in which international environmental law evolves. They address the functions of science in the law, the roles of private industry, and perspectives on how to attain desirable international outcomes. I then present a set of recommendations for improving the effectiveness of the law, recognizing the considerable challenges of fostering change in complex systems. Several of these account for changes expected in international policymaking; others I consider necessary independent of anticipated changes.