Missing-children posters usually list age, weight, height and eye color. But the Children's Identification and Location Database (CHILD) Project is concerned with just one identifier: the iris. The CHILD Project, which was announced last year, is a voluntary program that relies on iris scanning to help law enforcement find missing kids. The program kicks off in earnest this month when authorities in a half-dozen counties begin using the $25,000 scanning machines and feeding the registry. So far, 1,200 sheriffs' departments in 46 states have signed on; the CHILD Project hopes to have 3,000 systems in place nationwide, with 3 million to 5 million participants, in the next five years. While the focus for now is on kids, the system could eventually be used to track down Alzheimer's and mentally disabled patients. "It will be more accurate than fingerprinting, and it will be faster," says Col. Greg Brown of the Hillsborough County Sheriff's Office in Florida, which has joined the project. "This can be done in a matter of seconds."