Quentin Fiore, a graphic designer whose work helped magnify and popularize Marshall McLuhan’s maxim that “the medium is the message,” died on April 13 at a care facility in North Canaan, Conn. He was 99. Bianca Fiore La Porta, his daughter, said the cause was complications of bronchitis.

Mr. Fiore spent much of his career doing conventional design work for large corporations and book jackets for university presses. But he was best known for his book collaborations in the 1960s with McLuhan, the communications theorist, and later with the antiwar activist Jerry Rubin and the inventor and visionary Buckminster Fuller.