The euro set a record high against the dollar for the fifth session running on Wednesday and tested last year's lifetime high against the yen as investors' bearish views of the U.S. currency dominated markets.
Trading volumes were thin in the holiday period between Christmas and New Year.
There was also little news to turn investors' focus away from their worries about the burden of the U.S. current account deficit on the dollar and about the ability of the U.S. economy to attract enough money to plug this shortfall.
"The euro has been strong for a few days now. It is a repeat of late-2002 and late-2003," said Trevor Dinmore, foreign exchange strategist at Deutsche Bank in London.
"When you have low liquidity at the end of the year, you have fewer flows and you see more dollar weakness."
The euro gained about a quarter percent on the day to hit a record high of $1.3646. At 6 a.m. EST it stood at $1.3622.
It also strengthened against the British pound to reach its highest level in one year at 70.76 pence.
Against the yen, the euro traded at 140.85 yen, just below last year's record high around 140.90 yen.
The Swiss franc briefly lost some ground after Switzerland's leading KOF indicator fell much more than expected in December, hitting 0.49 which compared with expectations for a 0.68 reading.