I don't recall that he ever admitted so publically, although if you research the issue, you'll find a great deal of evidence that he was working at least in conjuction with the CIA. The agency definitely had a vested interest in popularizing the drug for the masses, and Leary fit the bill as their messiah. If you really look at it, before 1967 acid was widely promoted through the mass media in films, music, magazines, etc. All you have to do it connect the dots, the CIA wanted to test their wonder drug and we were just a nation full of willing lab rats.