The body of Kathleen Boyden, 32, an advertising saleswoman for WMAL radio who had been missing since last Thursday, was found decomposing in the back of her abandoned car yesterday on a quiet, residential street in Northwest Washington.

After an intensive, four-day search, D.C. police found the bloody, unclad body in the back of her 1980 Toyota shortly after 1 p.m. yesterday in the 3400 block of 17th Street NW in Mount Pleasant. D.C. Chief Medical Examiner Dr. James Luke said Boyden had apparently been bludgeoned to death.

Police late yesterday were seeking a warrant for the arrest of an unnamed suspect in the case.

Boyden was last seen Wednesday night by friends whom she visited to watch television. Telephone messages found in her apartment indicate she returned home between 11:00 and 11:30 that night.

After Boyden, known for her reliability, did not appear at work Thursday, several coworkers, along with her former roommate, Maysie Stewart, who had a key, went to Boyden's apartment. Boyden was not there, and neither was her car, usually kept in the basement garage of her apartment building, at 3040 Idaho Ave. NW.

After going to several of the restaurants where they believed she might have been eating dinner and finding no signs of Boyden or her car, they called police.

Several hours later, D.C. police entered the apartment and found evidence that someone had tried to wash blood off one of the walls. Bloodstains were also found in the stairwell leading to the garage.

At that point, police listed Boyden as a "critical" missing person and homicide detectives were assigned to assist the missing persons squad with the investigation because of the strong suspicion that the woman had met with violence.

During the intervening four days, officials at WMAL radio yesterday asked homicide detectives to allow them to broadcast a lookout for Boyden's car, hoping public attention would help find the car, and hopefully Boyden. Police, afraid that such publicity would scare away possible suspects, refused to let the station proceed with their announcements, however, according to station officials.

"At their [the police detective's] request, the story was being withheld," said WMAL executive vice president Andrew Ockershausen. "We just kept bugging them and asking when we could go with [the story]."

Finally, on Monday, after a police lookout for Boyden's car was apparently inadvertently broadcast over police radios and WMAL newscaster Gary Reels threatened to quit if he was not given permission to broadcast the story during his 5:30 p.m. news program, police issued a press release saying that Boyden was missing and inviting citizens with information to call the police.

Boyden's car was spotted yesterday afternoon by a workman who, upon hearing the broadcast, stopped to check the license plates on the car and then called the police.

After a police cruiser verified the location of the car, police dusted the car for fingerprints and then towed it directly to the medical examiner's office, where the body was removed.

Boyden was a graduate of Smith College, where she was president of her graduating class. She worked in New York and San Francisco before becoming assistant media coordinator for the U.S. Commission on the International Year of the Child and joined WMAL in 1979.