This excerpt taken from the C 10-Q filed Nov 5, 2007.
Fixed Income Credit Trading Losses
During the third quarter of 2007, Citigroup recognized approximately $636 million in credit trading losses due to significant market volatility and the disruption of historical pricing relationships. This was primarily a result of the sharp decrease in the sub-prime markets in both North America and Europe. The resulting trading losses are reflected in the Securities and Banking business.