For people convicted of a crack offense, the world of justice is unlike any other. Crack is simply cocaine processed so that it can be smoked. But federal law equates 5 grams of crack with 500 grams of powder cocaine, a 1-to-100 ratio that no other country recognizes. Possessing 5 grams of crack is a felony with an automatic five-year prison term, while 5 grams of the same drug in powder form is a misdemeanor likely to carry no jail time.

One consequence of the disparity is that kingpins at the top of a drug network who sell pounds of powder cocaine for processing often serve less time than street-level dealers who sell grams of crack.

"One of the great victims of the drug war is that our sense of penal proportion has been thrown out," said Zimring, of the University of California School of Law. "Now we have a fairness problem."

In addition, a law aimed at one type of drug use has been applied most often against one type of user -- urban blacks.

A higher percentage of blacks use crack cocaine than whites or Hispanic people. But in absolute numbers, twice as many whites as blacks use crack, and three times as many whites as blacks use powder cocaine, the national household survey shows.

As the war on drugs set up special penalties on crack, however, law enforcement focused on the highly visible, often violent crack trade in city neighborhoods, rather than the larger traffic in cocaine going on behind closed doors across the country. The result: Nearly 90 percent of the people locked up for crack under federal drug laws are black, McCaffrey said.

In state prisons, blacks make up nearly 60 percent of the people serving time on drug offenses, according to Justice Department figures, though they are only 12 percent of the general population and 15 percent of regular drug users.

"I don't think we got into this fix because of racism," McCaffrey said. "The impact of crack on the African-American community was devastating. And that's where enforcement has been concentrated."

The racial disparity would disappear if the law treated the powder and crack forms of cocaine equally, said Dr. Douglas McDonald, a senior scientist at Abt Associates, a social policy research group in Cambridge, Mass., who testified before Congress. If enforcement were evenly applied, more whites than blacks would go to prison, he said.

So for many blacks the legacy of crack is not just the violence and high prison rates that have hit so many communities, but a heightened sense that the law does not treat them fairly.

"You have so many people who feel hopeless, who feel that it is extremely unfair that so many low-level offenders are going to jail for such a long time," said Mattie Compton, a black community leader in Fort Worth, Texas, who is deputy chief assistant U.S. attorney for the civil division.

"We know we're going to lose people in poor neighborhoods, but when you see people who are prospects for future leaders going away to jail for so long, you wonder if we really are a community under siege," Ms. Compton said.

Asked about the legacy of crack in the Roxbury district of Boston, where he works with drug addicts at a community health center, Seward Hunter said: "If you're African-American, you expect to be targeted by the police and you expect to be stopped and searched."

Many in Congress say there is no racial intent behind the disparity between crack and powder. Crack is punished more severely because of the harm it does and because of the violent crimes associated with it.