NEW YORK (AP) _ Friends mourning the death of Pegeen Fitzgerald recalled how she and her husband, partners in a groundbreaking radio format, wove their way into the hearts of ardent listeners from Eleanor Roosevelt to average New Yorkers.

''If you listened to them, it seemed like you were eavesdropping on a conversation with a loving but not always an agreeing couple,'' said radio host John A. Gambling, who worked with Mrs. Fitzgerald and her husband, Edward, at WOR-AM.

Mrs. Fitzgerald, 78, died of breast cancer Monday in her apartment, said Roger Garner, a personal assistant. It was from that apartment that the Fitzgeralds most often broadcast their unscripted show - a program which featured discussions of the couple's everyday life, their friends and current events.

''They got mad at each other on the air. They celebrated things on the air,'' said Kathy Novak, a television producer who apprenticed with the Fitzgeralds. ''Pegeen always said, 'We don't read from any scripts.'''

The show, which first aired in 1937, ended with the death of Edward in 1982. Mrs. Fitzgerald continued on WOR for another year before moving to public radio station WNYC, where she was on the air until last spring.

The Fitzgeralds' program was the first of its kind, and quickly inspired an assortment of imitators.

The monthly bills could provide a show's worth of material. As the couple chatted, the sounds of their many pet cats or their cleaning woman running the vacuum could be heard in the background. Their only preparation for the program was a cursory reading of the newspapers and listeners' mail.

The couple's on-air arguments were the result of honest anger; Edward once became so upset during one breakfast show that he returned to bed and left his wife alone to finish the show.

''We're a true soap opera,'' she once remarked to a reporter.

Mrs. Fitzgerald first took to the airwaves when employees of a department store where she worked had to fill the air time of a store-owned radio station.

In 1937, a WOR-AM executive offered to put a microphone in her office at the store and she soon was doing a half-hour show during her lunch hour.

When she caught pneumonia, management asked if she could go on air from her hospital bed and later from her home while she was convalescing.

Because she did not want her announcer, Henry Morgan, to see her in a bathrobe, she asked if her husband could take his place. The husband-wife combination became a radio first, and First Lady Eleanor Roosevelt once went to their apartment to watch.

Ardent listeners protested vigorously whenever station executives tried to remove the Fitzgeralds from the airwaves. The listeners were so devoted to the couple that several willed their pets to the animal-loving couple.

Mrs. Fitzgerald was survived by four sisters and one brother.