This paper contributes to the literature on testing the random walk hypothesis by examining multiple variance ratio tests for emerging market exchange rates on a daily and weekly frequency. We have performed these tests using a bootstrap technique, which is robust to heteroscedasticity. We examine countries that have recently adopted floating exchange rate regimes, such as some Asian and Latin American countries, and analyze their recent behavior. Empirical evidence supports the random walk hypothesis on both a daily and weekly frequency. Furthermore, we test for longrange dependence and present evidence of structural breaks in generalized Hurst exponents. (c) 2006 Elsevier Ltd. All rights reserved.