he numbers give an inkling of the scope: One class-action suit. Two credit card issuers. More than 10 years. Thousands of pages of documents. Four million retailers. $13 billion in potential damages. Millions of consumers with debit cards.

Documents unsealed and released in the antitrust suit brought by retailers against Visa USA and MasterCard International, Inc. allege the two card issuers spent more than a decade discouraging competition and driving up costs to merchants.

The documents seem to support what participants, led by Wal-Mart and including most of the retailers in the U.S., allege in the suit. According to the documents, both credit/debit giants used a variety of tactics to undercut rival card issuers and undermine alternative forms of payment to ensure market dominance. These tactics included throwing their considerable market weight around, making big cash payments, some in the tens of millions of dollars, to banks for curtailing business with regional networks and slowing the distribution of PIN pads to merchants.

As consumers increasingly have used debit cards to make purchases, documents show Visa and MasterCard set out to force merchants into accepting signature-based offline debit cards, which result in higher transaction fees than online PIN-based cards. One internal Visa memo says, "Visa would like to see online disappear. Much bigger threat than AmEx." Another Visa strategy document from 1997 said, "It's time to declare war" on regional debit rivals; still another lists "Visa objectives" including "Prevent consolidation of debit business [and] block or disrupt formation of super-regional networks that may undercut Visa's brand dominance."

According to the documents, other card companies and merchants weren't the only targets. The documents allege the two card issuers also intentionally exploited consumer confusion about the branded debit cards and encouraged them to use signatures for transaction authorizations when using them.

Originally filed six years ago in U.S. District Court in Brooklyn, the suit was approved for class-action status by the Supreme Court in June 2002. The suit seeks an injunction against Visa and MasterCard to prohibit them from engaging in alleged antitrust violations as well as recovery of triple damages for the alleged excess fees paid on credit and debit transactions, which could total $13 billion. The trial is set to begin in April 2003.

The class includes any business that accepted Visa- or MasterCard-branded cards from October 1992 to the present. Retailers who wished to opt out of participation had until midnight Nov. 14, 2002 to request in writing removal from the class.