Wal-Mart Stores Inc. plans to roll out sophisticated electronic ID tags to track individual pairs of jeans and underwear, the first step in a system that advocates say better controls inventory but some critics say raises privacy concerns.

Starting next month, the retailer will place removable "smart tags" on individual garments that can be read by a hand-held scanner. Wal-Mart workers will be able to quickly learn, for instance, which size of Wrangler jeans is missing, with the aim of ensuring shelves are optimally stocked and inventory tightly watched. If successful, the radio-frequency ID tags will be rolled out on other products at Wal-Mart's more than 3,750 U.S. stores.

"This ability to wave the wand and have a sense of all the products that are on the floor or in the back room in seconds is something that we feel can really transform our business," said Raul Vazquez, the executive in charge of Wal-Mart stores in the western U.S.

Before now, retailers including Wal-Mart have primarily used RFID tags, which store unique numerical identification codes that can be scanned from a distance, to track pallets of merchandise traveling through their supply chains.