Anyone who has read more than a few books on Tibetan Buddhism will have encountered references to the Six Yogas of Naropa, a preeminent yogic technology system. The six practices - inner heat, illusory body, clear light, consciousness transference, forceful projection, and bardo yoga - gradually came to pervade thousands of monasteries, nunneries, and hermitages throughout Central Asia over the past five and a half centuries.<BR>Tsongkhapa (1357-1419) was a prolific writer and one of Tibet's greatest yogis and philosophers. His discussion of the Six Yogas is regarded as one of the finest on the subject to come out of Tibet. Glenn H. Mullin's study of the history, substance, and philosophical legacy of the Six Yogas of Naropa, together with his translation of Tsongkhapa's treatise, provides a guide to this tradition.