LOS ANGELES - Jack Valenti, 85, the former White House aide and film-industry lobbyist who instituted the modern movie-ratings system and guided Hollywood from the censorship era to the digital age, died yesterday.

Mr. Valenti had a stroke in March and was hospitalized for several weeks at Johns Hopkins University Medical Center in Baltimore. He died at his Washington home of complications from the stroke, said Seth Oster of the Motion Picture Association of America.

Mr. Valenti was a special assistant and confidant to President Lyndon B. Johnson when he was lured to Hollywood in 1966 by movie moguls Lew Wasserman and Arthur Krim. A lifelong film lover, he once cited A Man for All Seasons (1966) as his all-time favorite.

When he took over as president of the motion picture association, Mr. Valenti was caught between Hollywood's outdated system of self-censorship and the liberal cultural explosion taking place in America.

He abolished the industry's restrictive Hays code, which barred explicit violence and frank treatment of sex, and in 1968 oversaw creation of today's letter-based ratings.

"While I believe that every director, studio has the right to make the movies they want to make, everybody else has a right not to watch it," he said shortly before retiring in 2004. "All we do is give advance cautionary warnings and say this is what we think is in this movie."

Dan Glickman, his successor at the MPAA, said Mr. Valenti embodied the "theatricality" of the industry. "Jack was a showman, a gentleman, an orator, and a passionate champion of this country, its movies, and the enduring freedoms that made both so important to this world," he said in a statement.

The white-haired Mr. Valenti was familiar to movie fans through his appearances at the Academy Awards. He was equally animated whether testifying at a congressional hearing, hobnobbing at the Cannes Film Festival, or previewing films for Washington's elite in his office's private theater.

In Mr. Valenti's later years, he handled tricky new challenges from the Internet and technologies that allow movies to be illegally reproduced and distributed in an instant. He also traveled worldwide seeking to thwart movie piracy.

He and his wife, Mary Margaret Wiley, had three children.