Managing the benefits and costs associated with reactive nitrogen is one of the most dynamic challenges society faces today. On one hand, reactive nitrogen is an essential resource. Its use in agriculture has undoubtedly increased the availability of food, fiber, and feed and contributed to major advances in human well-being over the last half century. On the other hand, human additions of reactive nitrogen to the environment now dominate the global nitrogen cycle. The increased quantity of reactive nitrogen in the air, water, and soil is causing significant changes to the environment (climate change, air and water pollution, and biodiversity loss) and threatens the health and vitality of human and natural resources worldwide. But while the challenges reactive nitrogen presents to society are clear, the most appropriate responses are less apparent. Solutions will need to balance trade-offs among ecosystem services and the competing objectives of key actors. This symposium brings together biologists, biogeochemists, and economists to discuss the frontiers of knowledge and solutions on this pressing issue. Speakers will report on the results of domestic and international assessments that link nitrogen science, practice, and policy at a variety of locations and scales.