Ever wonder how Wal-Mart can charge next to nothing for items that cost a bundle at other stores? According to some disgruntled workers, Wal-Mart's penchant for paying women less than men could be a reason for those notoriously low, low prices. On Monday, the largest class-action employment lawsuit in U.S. history was given the green light to head to trial by a federal appeals court. The 9th U.S. Circuit Court of Appeals based in San Francisco ruled the combined multiparty litigation is certified to move forward to trial. The split 6-5 ruling by the court to advance the case to trail could potentially cost Wal-Mart billions of dollars.

At the center of the lawsuit are allegations of unfair pay, discrimination and gender bias. The plaintiffs claim women employed by the super store were paid lower wages than their male counterparts and were subsequently denied promotion opportunities throughout the company. The plaintiffs seek back pay and punitive damages against the globe's largest international retail conglomerate. According to the lawsuit, the company's "strong, centralized structure fosters or facilitates gender stereotyping and discrimination." Women make up roughly 70 percent of Wal-Mart's hourly work force but over the last decade only a tiny one-third of its management.

Betty Dukes, a store greeter in Pittsburg, Calif., along with five of her co-workers first filed the lawsuit in 2001. Since that time, the case has exploded, with thousands of women's names added to the plaintiffs list. The court concluded that there was enough merit to the claims of Dukes and the others in the lawsuit to proceed to trial on a class-action status. Class action status for the lawsuit ups the ante financially and judicially, since more plaintiffs now can join the lawsuit. Discovery hearings hosted by both sides of the lawsuit led to Judge Susan Gruber's approval of class-action status, despite the size and scope of the case.

Wal-Mart has been plagued with labor lawsuits and disputes for years. The company already has settled and shelled out $6 million in 13 different lawsuits alleging discriminatory treatment of African-American truck drivers and workers with disabilities.