Lead plaintiff Shirley "Rae" Ellis, a Costco assistant warehouse manager, alleges that the Issaquah, Washington-based, retailer does not announce openings for higher-paying managerial jobs, but relies instead on a "tap on the shoulder" by top-level male executives-- a system which consistently picks men rather that women for higher-level positions. Although Costco's U.S. workforce of 78,000 is nearly 50% female, allegedly fewer than 1 in 6 senior managers are women. Ellis alleges that she was promised rapid promotions at Costco and received glowing reviews, but was repeatedly denied promotion to warehouse manager positions. She allegedly learned about many of the openings only after they were filled. After Ellis filed a discrimination charge with the EEOC in 2002, she was allegedly retaliated against by Costco and transferred to a new warehouse far from her home.

Class-action employment claims make up only a small part of the 40,000-plus federal civil rights cases filed every year, and they are hard to track because they are filed all over the country. Federal statistics suggest that the actions have been climbing slowly over the past decade or so. In fiscal 2003, employees filed 76 federal class-action claims, only slightly more than the 74 filed in 2002, but more than double the 32 filed in 1991, according to the Administrative Office of the U.S. Courts.