This volume is a translation of the first twelve chapters of ( ), along with the commentary called ), a commentary in Sanskrit on this tantra by the seventh-century Buddhist intellectual and tantric scholar-adept Chandrakirti. Regarded by Indo-Tibetan tradition as the esoteric scripture wherein the Buddha revealed in greatest detail the actual psycho-physical process of his enlightenment, is a preeminent text of the class of scriptures known to Indian Buddhist scholar-adepts as great yoga tantra, and later to their Tibetan successors as unexcelled yoga tantra. presents a system of interpretive guidelines according to which the cryptic meanings of all tantras might be extracted in order to engage the ritual and yogic practices taught therein. Applying its interpretive strategies to the text of , articulates a synthetic, “vajra vehicle” ( ) discourse that locates tantric practices and ideals squarely within the cosmological and institutional frameworks of exoteric Mahayana Buddhism.