This thesis examines two key areas where macroeconomic policy and stability in international financial markets intersect. Part one examines the extent to which economic policy can limit the development of misalignments in exchange rates, without sacrificing policy tools that are needed to maintain internal macroeconomic balance. This issue is addressed in a model where endogenous exchange rate fluctuations are generated by traders selecting alternative forecasting strategies on the basis of an ‘evolutionary fitness rule’, in the spirit of work by Brock and Hommes (1997, 1998). In this setting it is shown how, by changing the relative profitability of available strategies, sterilized intervention can coordinate traders onto strategies based on macroeconomic fundamentals. Empirical evidence in support of the model is provided based on data from interventions by the Japanese authorities in the 1990’s. In addition, simulations of the estimated model are used to calculate confidence intervals for the ex ante probability that interventions of a given size will be effective in pricking bubbles in the exchange rate. Part two moves on to examine the implications for macroeconomic policy of the exponential growth in recent years of the use of financial derivatives. A theoretical model is developed which demonstrates how firms’ use of derivatives for risk management purposes, while increasing the robustness of the financial system to shocks, at the same time reduces the impact of monetary policy on the macroeconomy. This effect arises because the agency costs, which enhance the impact of monetary policy through the credit channel, are reduced by firms’ usage of hedging instruments, in particular interest rate swaps. Using quarterly data on total outstanding swap contracts from 1990, empirical evidence is then presented to show how increased usage of derivatives may have influenced the impact of monetary policy in the United States.