In a closely watched case, a sharply divided federal appeals court on Monday ruled 6-5 that a sex discrimination lawsuit against Wal-Mart could proceed as a class action for more than a million women. The suit is the biggest employment discrimination case in the nation’s history.

After a decade of pretrial maneuvering, the decision by the United States Court of Appeals for the Ninth Circuit, in San Francisco, was a victory for the plaintiffs. It hastens an eventual trial for the women,, who are seeking billions of dollars from Wal-Mart, the world’s largest retailer.

“Wal-Mart tries to project an improved image as a good corporate citizen,” said Brad Seligman, a lawyer for the plaintiffs. “No amount of P.R. is going to work until it addresses the claims of its female employees.”

The lawsuit, brought in 2001, accuses the retailer of systematically paying women less than men, giving them smaller raises and offering women fewer opportunities for promotion. The plaintiffs stressed that while 65 percent of Wal-Mart’s hourly employees were women, only 33 percent of the company’s managers were.