Two of the girls - a 16-year-old and an 18-year-old - had "Mr. Cream" tattooed on their bodies.

It was just one of the ways that Mr. Cream, whose real identity is Victor Powell, told the three girls he pimped that they belonged to him, federal prosecutors say.

He also is accused of moving them from motel room to motel room, raping and beating them. All of it kept them in line for months as he peddled their bodies on a "stroll," where men drive by trolling for prostitutes, according to the FBI. Like most pimps who traffic in underage girls, Powell, 22, also took his juvenile prostitutes on the road to Minnesota, St. Louis and Arizona, prosecutors allege.

And they say when he crossed state lines, Powell opened the door to federal prosecution. The FBI and U.S. attorney now plan to make an example of Mr. Cream.

The case is the first-ever federal prosecution of juvenile sex trafficking in Chicago. FBI agents hope it will prove a powerful symbol to criminals who are now the top priority of the bureau's criminal-investigation division, said FBI Assistant Director Chris Swecker, who heads that department.

A federally funded 2001 study by University of Pennsylvania researchers found that at least 325,000 American children are victims of some form of prostitution. A local study in 2002 estimated the number of prostitutes in the Chicago area at 16,000. Of those prostitutes interviewed in the Center for Impact Research's study, a third said they started trading sex for money before the age of 15.

The FBI estimates the average age of a prostituted child is 13, and most investigators have seen preteens peddled by pimps.