The State Department, which in recent years has been ringed by dump trucks and fortified by concrete barriers and electronic devices against possible terrorist attacks, adopted new security measures yesterday affecting all visitors to the massive building at 22nd and C streets NW.

The procedures, put into effect hours after a 20-year-old man entered the building and shot and killed his mother in a seventh-floor office, will curtail the ready access that had been granted to family members of workers, members of the news media and employes of private concerns located in the building.

Under the new procedures, which State Department officials said were being "tightened . . . as a result of the unfortunate security incident," only persons holding permanent State Department or U.S. Agency for International Development passes will be able to enter the building without passing through metal detectors.

Edward Steven Doster, whom D.C. police said shot and killed his mother, 44-year-old Carole Doster, before fatally wounding himself, apparently used a dependent's pass to bypass the electronic surveillance.

The dependents' passes are temporary passes issued for two years.

Reporters accredited to the State Department were required to pass through electronic detectors for the first time.

Each of the four pedestrian entrances to the building, which stretches from 21st to 23rd streets NW and from C Street to a ramp for the E Street Expressway, has been equipped with the electronic detectors. Previously, only the 21st Street entrance and the main diplomatic entrance on C Street -- through which Doster passed -- had the devices.

In addition, the State Department notice said, all vehicles entering the building's parking garages will be stopped to ensure the vehicle has a department parking pass and that all the occupants have permanent State Department identification cards.

Any person in a car who does not have an ID card will have to leave the vehicle and enter the building through a pedestrian entrance.

At a background briefing yesterday afternoon, a senior department official said that on a typical day there are 10,000 persons who enter the building. There are 7,000 State Department employes with permanent passes, he said.

They are issued after a full-field investigation of the employe, a review of references and an investigation of the employe's dependents.

"I think we have good security," the official said. However, he said, "It's possible for an employe to walk in here with a weapon and shoot somebody. We have to function here . . . . I don't think you can ensure that a tragic accident like this will never happen."