The big money of high finance occasionally brings on bad bets and spectacular frauds. Which of those apply to Switzerland's UBS isn't yet clear. On Sept. 15, UBS said it had suffered a $2 billion loss from "unauthorized" trading in its London equities unit. Kweku Adoboli, a trader with UBS's investment bank, was arrested by London police and charged with fraud and false accounting in connection with the trading loss.

The UBS debacle appears to be the latest example of traders costing their firms fortunes. Some such "rogue traders" write books about their experiences—as did Barings Bank's Nick Leeson and Daiwa Bank's Toshihide Iguchi. Others start new ventures.

What follows is a look at some of the worst financial losses from unauthorized trades over the past 20 years.
Photographer: Bloomberg