Sometimes evidence of the still-omnipresent glass ceiling pops up in unlikely places, like your local discount store. Massive chains like Wal-Mart are known for great deals and low prices that drives competitors out of business while shoppers flock to pick up incredible values. Thousands of female Wal-Mart employees, however, say the super store also is famous for gender bias and discrimination.

This week, the largest class-action employment lawsuit filed in U.S. history was granted class action status by the 9th U.S. Circuit Court of Appeals in San Francisco. The 6 to 5 ruling will give more than 1 million former and current female employees of Wal-Mart their day in court. By achieving class-action status, the lawsuit could cost Wal-Mart billions of dollars in damages, legal fees and projected settlement costs.

The massive discrimination lawsuit claims that women workers of the world’s largest retail chain were paid lower and given fewer management opportunities than their male co-workers. The plaintiffs claim that men employed by Wal-Mart systematically earn higher wages and receive promotions despite the sheer number of women Wal-Mart has in its workforce. According to the lawsuit, the company sent a clear message to their female employees: management is for men and not women. Betty Dukes of Pittsburg, Calif., is named as the lead plaintiff in the lawsuit. Dukes first filed a suit against Wal-Mart in 2001 with six other Wal-Mart employees who worked at 13 of the company’s 3,400 nationwide stores. Dukes and her co-plaintiffs are seeking back pay and punitive damages.

Wal-Mart adds its name to a shameful list of national businesses accused of gender bias and discrimination in 2010. Banking giant Goldman Sachs, airline Jet Blue and Bank of America are among the companies facing high-profile gender discrimination lawsuits.