1BR note, replaced the Soviet rouble in 1992. Changing American dollars into Belarusian or Russian roubles is not a problem. Other currencies present more difficulties. Torn or marked notes and dollar bills issued before 1990 are generally not accepted. If you want to exchange your roubles back to dollars though it's nearly impossible to do so in banks.
Private individuals are more likely to buy dollars.
But beware that changing money on the street is illegal and punishable. VISA and Mastercard credit cards and more rarely American Express and Eurocard are accepted at select hotels, restaurants and shops, but in general it s better to rely on cash. VISA, Thomas Cook and American Express traveller s cheques can be changed in banks, but are useless as tender in the retail world. Currency exchanges abound and many people will offer to change your dollars into roubles for you. Apart from a growing number of 24-hour food stores most shops are closed on Sundays and official holidays.