Deutsche Bank has issued a profits warning, saying it made an estimated loss of 4.8 billion euros ($US6.4 billion) in the fourth quarter last year.
It said the loss reflected "exceptional market conditions", which hit its sales and trading businesses.
Deutsche Bank expects a full-year loss for 2008 of about 3.9 billion euros.
Fourth-quarter and full-year earnings are due to be issued on 5 February.
Despite the tough conditions, Deutsche Bank is still buying a stake in Postbank. On Wednesday, it was announced that, under a new deal between the banks, Deutsche Bank will now buy 22.9% of Postbank.