The Supreme Court on Monday agreed to hear an appeal in the biggest employment discrimination case in the nation’s history, one claiming that Wal-Mart discriminated against hundreds of thousands of women in pay and promotion. The lawsuit seeks back pay that could amount to billions of dollars.

The question before the court is not whether there was discrimination but rather whether the claims by the individual employees may be combined as a class action. The court’s decision on that issue will almost certainly affect all sorts of class- action suits, including ones asserting antitrust, securities and, products liability and other claims.

If nothing else, many pending class actions will slow or stop while litigants and courts await the decision in the case.

“We are pleased that the Supreme Court has granted review in this important case,” Wal-Mart said in a statement. “The current confusion in class-action law is harmful for everyone — employers, employees, businesses of all types and sizes and the civil justice system. These are exceedingly important issues that reach far beyond this particular case.”

Brad Seligman, the main lawyer for the plaintiffs, said in a telephone interview after the court decision: “Wal-Mart has thrown up an extraordinarily broad number of issues, many of which, if the court seriously entertained, could very severely undermine many civil rights class actions. We welcome the court’s review of this limited issue, and we’re confident that the core of our action will go forward.”