The national currency of Mongolia is tugrug. Bank notes are issued for 20.000; 10.000; 5.000; 1000; 500; 100; 50; 20; 10 tugrug denominations.  Foreign currency can be exchanged at commercial banks through their branches and counters in the major hotels and international airport. It is recommended carrying a certain amount of US$ cash that is accepted for local currency. Major hotels and restaurants and tourist shops now accept credit cards. American express, VISA and Master cards are the most widely accepted. It is also possible to change travelers check and get cash advances on your credit card. At several banks and countless licensed money changers in Ulaanbaatar, you can change most major European and Asian currencies. The US greenback is still the easiest to change in Ulaanbaatar, and is the only currency you might be able to change in the countryside. Note that moneychangers will give you slightly better rates for new (ie, post-1996) US dollar bills and for higher denominations (US$50 and US$100). US dollar bills dated pre-1988 are difficult to exchange any-where. In the countryside however anything larger than a US$20 will be hard to change.  American dollars can sometimes be changed for tugrug at banks in aimag capitals but it is bound to take forever as officials try to find out the exchange rate, which is likely to be considerably lower than in the capital.