He did more than smoke cigars and leer at women. He defended free speech and U.S.-Soviet friendship. He had opinions on everything from the New Deal to the United Nations.

So when Groucho Marx wiggled those eyebrows and made wisecracks about the Establishment, a few Establishment eyebrows went up as well.

Documents recently made public show that the FBI kept detailed files on the comedian, ranging from his supportive quote about the Scottsboro Boys in the 1930s to jokes made on television in the 1950s and '60s.

With the unintentional humor of a Marx Brothers villain, the bureau is still withholding several pages "in the interest of national defense or foreign policy."

"In 1953, the FBI was told by one of their confidential informants that Groucho was a member of the Communist Party and they decided to do a full review," said Jon Wiener, the University of California at Irvine history professor who acquired the files through the Freedom of Information Act.

"Getting the files on Marx was a kind of shot in the dark. I had been a plaintiff in a lawsuit to the John Lennon FBI files," Wiener said. "We recently settled most of the issues in that case so I thought, After Lennon, why not Marx?' "

The son of Jewish immigrants, Marx grew up in turn-of-the-century Manhattan, in a world where socialism was about as subversive as the Sabbath, and he became a dependable member of Hollywood's liberal community.

But what was standard left-wing thinking in the 1930s and '40s became suspicious thinking in the Cold War era. In 1953, the House Un-American Activities Committee (HUAC) pressured Marx through Jerry Fielding, bandleader for the comedian's TV game show, "You Bet Your Life."

Fielding, who had been tagged as a Communist sympathizer in Walter Winchell's column, later said the committee wanted him to name Marx as a fellow traveler. Fielding refused and the show's sponsor, DeSoto-Plymouth Dealers of America, persuaded Marx to fire him.

"That I bowed to sponsors' demands is one of the greatest regrets of my life," Marx wrote later.

According to the FBI files, Marx's alleged offenses date to a 1934 article in the Communist Party newspaper the Daily Worker. The article claimed that he called Communist support for the Scottsboro Boys an inspiration for "Soviet America."

In the 1940s, Marx attended a benefit concert for Soviet war relief, helped sponsor a fund-raiser for the liberal magazine The Nation and opposed United Nations recognition for the fascist government of Spain. He also was a member of the Committee for the First Amendment, an anti-HUAC organization that included Frank Sinatra, Humphrey Bogart and Lauren Bacall.

"You Bet Your Life" was a popular program, but the Groucho files are filled with letters from unhappy viewers in the 1950s and '60s. One letter complained that when a guest told Marx he was a former pugilist and bootlegger, the comedian responded, "You mean you were a bootlegger for the FBI?" Another writer observed that "Groucho Marks" had referred to the United States as "the United Snakes" and was friendly with another alleged Communist sympathizer, Charlie Chaplin.

There is no indication that Marx's career was affected, but the FBI did take him seriously. One internal memo -- noting that Marx's real name was Julius H. Marx -- was initialed by six officials, and then-FBI director J. Edgar Hoover personally responded to at least one letter, enclosing the pamphlet "What You Can Do to Fight Communism and Preserve America."

Entries to Marx's file ended in the early 1960s. He died in 1977.

"They concluded from their study he was not a member of the Communist Party," Wiener said. "The party was a very rigid organization; it's hard to imagine a wisecracking spirit like Groucho's in it."