District of Columbia police officials and local business executives began a campaign yesterday to raise $500,000 to buy bulletproof vests for the department's 3,000 street-level police officers.

The effort is the result of the shooting deaths of two D.C. officers in the line of duty over the last five months, campaign organizers said. If the 21 officers who have been killed in the line of duty the last 20 years had been outfitted with vests, many could have been saved, police officials said.

"It's very difficult to go to families, wives and next-of-kin to tell them that their brother, sister, or son has been killed in the line of duty," the Rev. R. Joseph Dooley, police chaplain, said at a press conference yesterday. Dooley said the last time he talked with the wife of a policeman who had been fatally shot, "she wanted to know why her husband didn't have a vest. We're trying to answer that question today."

The group of executives and police officials organizing the drive said $15,000 had been raised from corporate and individual donors in recent weeks, and $7,500 more was raised during yesterday's press conference at police headquarters.

The group's organizers said they will obtain the vests at manufacturer's cost, $150 each. Officers demonstrated the vest yesterday at the department's crime laboratory by shooting a .38 caliber bullet into a vest on a dummy. The slug was flattened and lodged among the layers of the vest, but did not go through it.

Mayor Marion Barry said he had given $200 of his own money to the campaign. "Because of the tough budget times we're having," Barry said, "it's going to be up to our citizens to understand the need" for the vests.

Officers in every county and jurisdiction surrounding the District already have vests, police officials said.

Since December, the D.C. police have been using 160 vests on a trial basis. The first day the vests were in use, an attacker tried to stab Officer Rufino Fisher on Corcoran Street NW with an eight-inch butcher knife, but none of the three knife thrusts penetrated Fisher's vest, poice said.

Two months ago, Officer Robert K. Best, 24, one day after completing his rookie year, was shot during a struggle with a suspected car thief. On Sept. 14, Officer Donald G. Lunning, 31, an 11-year veteran, was shot fatally in the chest in a struggle with a man he believed was driving a stolen car.