In this chapter, balance-of-payments equilibrium relates to the position of a single country, primarily the USA. US equilibrium is evidently affected by changes in other countries, both separately and in the world as a whole. It is also related to the world payment system. But equilibrium for particular countries need not imply equilibrium for the system. The system's equilibrium, for example, may require the net of the surpluses and deficits of the separate countries to be either zero, given adequate reserves, or a substantial surplus. The criteria for determining balance-ofpayments equilibrium, therefore, may or may not converge with those of the system as a whole.