http://www.jesus-is-savior.com/False%20Religions/Scientology/aleister_crowley.htm
Russell Miller has adequately chronicled Hubbard's connection in 1945 to John W. Parsons, who headed Crowley's Ordo Templi Orientis chapter in Los Angeles. (2) Hubbard was an active member in this group for several months, and first met his second wife there. The Church of Scientology claims that Hubbard was actually infiltrating this group in order to break it up, but the following should suffice to dismiss this claim.
In the Philadelphia Doctorate Course lectures taped in 1952, Hubbard discusses occult magic of the middle ages, and recommends a current book - "it's fascinating work in itself, and that's work written by Aleister Crowley, the late Aleister Crowley, my very good friend." The book recommended was The Master Therion, (published in London in 1929) later re-released as Magick in Theory and Practise. L. Ron Hubbard, Jr. asserts that during the time when the Philadelphia course was given his father would read Crowley's works "in preparation for the next day's lecture…"