Some of the files deal with what the FBI describes as "obscene material" published in the early days of the magazine. The FBI interviewed Hefner about the magazine.
Hefner was arrested at his Chicago home on obscenity charges in 1963 and acquitted by a jury.
Hefner published the first issue of "Playboy" in 1953. He died in 2017 of natural causes at age 91.
To see the files on Hefner released by FBI, click here.