With new companies continuing to jump on the radio frequency identification bandwagon, spending on the technology increased by 39% last year, according to a recent study.

Spending topped $500 million in 2005, said Jeff Woods, vice president of research at Gartner Inc., Stamford, Conn., a research and advisory firm.

The increase has mainly been driven by retailers, Woods said.

"There are a number of retailers that are pushing their suppliers to expand the use of RFID," Woods said. "Additionally, the military's use of active RFID tags on containers continues to expand. There are hundreds of other pilot projects taking place, too."

In December, Wal-Mart Stores Inc., Bentonville, Ark., said it would begin sharing Electronic Product Code data with 13 manufacturers.