WASHINGTON — Immigrants — both legal and illegal — do not raise the rate of crime in the United States, according to a study released Monday.

In every ethnic group, incarceration rates among young men are lowest for immigrants, even those who are less educated, said the study by the Immigration Policy Center, an immigrant-advocacy group in Washington. This holds especially true for Mexicans, Salvadorans and Guatemalans, who make up the bulk of the illegal population.

The authors of the study say it dispels the common notion — which they say is propagated by excessive media coverage of crimes and gang activity — that immigrants commit crimes at higher rates than native-born Americans.

"The misperception that immigrants, especially illegal immigrants, are responsible for higher crime rates is deeply rooted in American public opinion and is sustained by media anecdotes and popular myth," said Ruben G. Rumbaut, a sociology professor at the University of California-Irvine. "This perception is not supported empirically. In fact, it is refuted by the preponderance of scientific evidence."

The incarceration rate of U.S.- born men 18 to 39 years old in 2000 was 3.5 percent — five times higher than the incarceration rate of their immigrant counterparts, the study found.

The report — which analyzed data from the U.S. Census Bureau, police records and other sources — also shows that a large increase in illegal immigrants has not resulted in a rise in crime. Since 1994, violent crime in the United States has declined 34 percent, and property crime has fallen 26 percent. At the same time, the illegal immigrant population has doubled to around 12 million.

The study also details a "paradox of assimilation" in which second- and third-generation immigrants have higher crime rates than those who first come to the United States.

For example, foreign-born Mexican men had an incarceration rate of 0.7 percent in 2000, more than eight times lower than the 5.9 percent rate of U.S.-born males of Mexican descent.

The study concludes that the children and grandchildren of many immigrants become subject to economic and social forces, such as higher rates of family disintegration and drug and alcohol addiction, that increase the likelihood of criminal behavior.

Steve Camarota, director of research at the Center for Immigration Studies, a Washington think tank that advocates lower levels of immigration, said the impact of high immigration on crime will not be known for a long time because children born to recent immigrants are still growing up.

"On the issue of crime, the biggest impact of immigration is almost certainly yet to come," he said.