The House passed and sent to President Bush legislation establishing a national Internet database designed to let law enforcement and communities know where convicted sex offenders live and work.
Attorney General Alberto Gonzales applauded its passage. "America's children will be better protected from every parent's worst nightmare — sexual predators," he said.
The most serious offenders would be registered on a national database for a lifetime. All sex offenders could face a felony charge, punishable by 10 years in prison, for failing to update the information.
"This legislation would make it crystal clear to sex offenders: You better register, you better keep the information current, or you're going to jail," said Rep. James Sensenbrenner, R-Wis.
The House passed the bill by voice vote. The Senate approved it with a voice vote last week.
Sensenbrenner, chairman of the House Judiciary Committee, said there are half a million sex offenders in the United States and as many as 100,000 are not registered, their locations unknown to the public and police.
Convicted criminals required to register will have to do so, in person, in each state where they intend to live, work or go to school.
"It's time for all of our families to have access to this information," said Rep. Earl Pomeroy, D-N.D.
Child advocates have said the bill offers the most sweeping effort to combat pedophiles in years. It's named for Adam Walsh, the murdered son of "America's Most Wanted" host John Walsh.
"We used to track library books better than we do sex offenders but this bill will even that score," said Rep. Mark Foley, R-Fla.
One initiative would create a demonstration project requiring sex offenders to wear tracking devises during their supervised releases.
The bill increases criminal penalties for child predators, including a mandatory minimum 25-year prison sentence for kidnapping or maiming a child and a 30-year sentence for sex with a child under 12 or for sexually assaulting a child between 13 years old and 17 years old.
A new racketeering-style offense for people who commit two or more crimes against children would carry a mandatory 20-year sentence. Repeat child sex offenders would face harsher penalties.
The bill also authorizes new crime prevention and child fingerprinting campaigns, along with new grant programs to combat the sexual abuse of children.