By January 2007, the company expects that 600 of its suppliers will be using RFID technology and that the number of Wal-Mart stores capable of handling RFID-tagged items will have doubled to about 1,000.

Walton noted that Wal-Mart has seen a return on its RFID investment -- even before any extensive process changes have been put in place.

For example, she said, out-of-stock items carrying RFID tags are being replenished three times faster than they were before the project began. However, she didn't disclose how much money Wal-Mart has saved by using RFID.

One RFID project that's still in a proof-of-concept phase involves adding sensor tags to perishable goods such as fruit. Wal-Mart is using a special tag to track just how long a crate of, say, bananas has been in transit, so it can ensure that it's sold when the fruit is ripe, Walton said.

Later this year, Wal-Mart will launch a pilot project that tests whether RFID tags can be used to improve the efficiency of unloading boxes from trucks, Walton said.