Diversification is widely practiced by investors seeking to reduce risk. In recent years investors have been turning to foreign markets to obtain even greater scope for diversification than domestic markets offer. With the internationalization of security portfolios, however, also comes an additional risk-foreign exchange risk. ; The use of currency derivatives in internationally diversified portfolios can help mitigate foreign exchange risk. This article investigates the impact of currency hedging on these portfolios, in particular index portfolios of stocks and bonds from markets in seven industrialized countries. The author finds that the apparent risk-reducing benefits of currency hedging of equity portfolios in the early 1980s did not continue into subsequent periods. In contrast, foreign long-term bond portfolios consistently exhibited dramatically lower variability of hedged returns compared with unhedged returns. The case for (or against) currency hedging is not decisive, though, because the lower variability of hedged returns historically is associated with lower returns. The decision to hedge depends on the investor's preference for risk and return.