AbstractSwap rate risk, also called the problem of' “maturity gaps,” originates from foreign currency holdings whenever the involved contracts have differing maturities. Such differing maturities give rise to a sensitivity of the portfolio values with respect to the “swap rate,” or differential between the relative interest rates in two countries. Volatility risk, which typically affects only currency contracts having asymmetric payoffs (such as currency options), gives rise to a sensitivity of portfolio values with respect to changes in the exchange rate volatility. In this article we show how currency portfolios may beimmunized, or made insensitive, to both swap rate risk and volatility risk, in the sense of Macaulay's (1938) classical treatment of interest rate risk. The European currency option contract is the primary subject of our discussion, since we show that both ordinary forward contracts and other complicated currency contracts are equivalent to suitable combinations of European currency