The concept of global public goods has drawn increasing attention in the past decade, although in truth it has been known for over a century with regard to the prevention of the spread of contagious disease (and for much longer with respect to the avoidance of war). The essence of such goods is that they benefit all nations, although perhaps not equally. The Johns Hopkins economist Barrett provides a useful taxonomy of the requirements for public goods. Some (deflecting a meteor headed toward earth) can perhaps be supplied by a single competent state; others (the eradication of smallpox) depend on effective action in all the relevant states, however weak; still others (mitigating global warming) require action by all states. Some require action; others (nuclear weapons tests or nonproliferation) require agreed inaction. The instrument of cooperation is typically a treaty among sovereign states, although some cooperation, especially the coordination of standards and measurements, has been accomplished without formal treaties. Many (but not all) public goods are expensive, raising the issue of who shall pay and creating "free rider" incentives for many or even all states. Inadequately provided global public goods offer a rich agenda for the future; the relevant issues, along with many historical examples of both successes and failures, are intelligently addressed here.