A $75 million settlement has been approved between American Express Co. and thousands of cardholders who contended in a class-action lawsuit that they paid hidden transaction fees for charges made in foreign currencies.

The settlement, approved this week by U.S. District Judge Cecilia M. Altonaga, affects more than 833,000 cardholders who paid some form of transaction fee from March 28, 1997, through Oct. 15, 2004. Settlement amounts could range from $15 to millions of dollars, lawyers involved in the case said Friday.

The lawsuit, initially filed in state court in August 2003 and then transferred to federal court, claimed that American Express failed to adequately inform cardholders that they would be charged an adjustment of up to 2 percent for the conversion of charges made in foreign currencies to U.S. dollars.