The first step in designing effective policies to stabilize an economy is to understand business cycles. No country is isolated from the world economy and external shocks are becoming increasingly important. The author documents the sources of macroeconomic fluctuations in 22 emerging-market countries, and measures two specific shocks that could be transmitted from one country to another: a world real output shock and a world real interest rate shock. Her analysis shows that there are major differences in the transmission mechanism across emerging-market countries. To assess whether they are due to different economic structures or to the exchange rate regime, she divides the sample into groups of countries. The results indicate that the exchange rate regime is a critical factor, although restrictions on capital flows also play a crucial role. The author also shows that regional groups and trade openness do not play as important a role as the exchange rate regime and capital flows in determining the transmission of business cycles.