This is the first book in a series presenting The Great Exposition of Secret Mantra. The other two books are Deity Yoga and Yoga Tantra. Tantra in Tibet consists of three parts published under the auspices of the Dalai Lama. "Essence of Tantra" by the Dalai Lama discusses tantra for practice, refuge, the three paths, greatness of mantra, clear light, and initiation. "The Great Exposition of Secret Mantra--Part 1" by Tsongkhapa is one of the principal classic texts on tantra. It presents the main features common to all the Buddhist tantra systems as well as the differences between sutra and tantra. In this volume Tsongkhapa covers paths to Buddhahood, vajra vehicle, deity yoga, and method in the four tantras. "Supplement" by Jeffrey Hopkins discusses the meaning of emptiness, transformation, and the purpose of the four tantras.