Many countries have multiple exchange rate regimes, with black or secondary currency markets operating alongside an exchange rate pegged or determined in interbank or auction markets. Leakages occur across these markets, necessitating careful analysis of the dynamic effects of numerous policy instruments. Using a model with multiple exchange rates and leakages, we trace the dynamic effects on official and parallel foreign exchange markets of exchange rate unification, changes in foreign exchange surrender requirements, taxes on trade and capital account transactions, and official exchange rate devaluation. Simulations based on Russia's recent experience demonstrate the qualitative importance of the results.