The number of homicides fell last year for the first time since 1999, part of a nationwide decline in all types of violent crime, according to preliminary FBI data released yesterday.

Cities with more than 1 million people had the greatest decrease in violent crime, 5.4 percent, while cities of fewer than 10,000 saw the biggest drop in homicide, 12.2 percent.

Homicides fell by 3.6 percent from the 16,500 reported in 2003, meaning there were nearly 600 fewer. Chicago was largely responsible for the drop.

The city led the nation in homicides in two of the three previous years, so leaders there launched a law enforcement effort that drove down the number of homicides from 598 in 2003 to 448 last year.

In Washington, the preliminary numbers show a 17 percent drop in violent crime and a 20 percent decline in homicides, from 248 in 2003 to 198 in 2004. The report did not include data for the Maryland and Virginia suburbs. In Baltimore, violent crime rose by 4 percent, and homicides increased by about 2 percent, from 270 to 276.

Criminal justice experts say the nationwide decline in violent crime is something of a surprise because gang-related activity is increasing in some parts of the country, the economy is sputtering in some areas, the number of at-risk youth is rising and law enforcement budgets are being cut.

With more than 12,700 law enforcement agencies reporting, the FBI's preliminary data show the number of violent crimes decreased 1.7 percent in 2004 compared with 2003, while property crime fell 1.8 percent.

Violent crimes are rape, robbery, aggravated assault, and homicide, including murder and manslaughter. Property crimes include burglary, larceny/theft and car theft. Every category saw a drop from 2003. Arson, measured separately, saw the biggest drop -- 6.8 percent.