[page 96] The tantric division comprises several hundred titles in some twenty-two of the 108 volumes of works included in the bKa' 'gyur.3 These tantric texts represent a variety of works that are different in both length and content, and have diverse titles. The overall length of tantric texts varies considerably. Some are very short, comprising a few folios or even less, but on the whole their length varies between twenty and over one hundred folios, with only a few texts extending over two hundred. Like the sūtras the tantric texts are written in the form of dialogues or instructive expositions which are in prose or verse, but most frequently in mixed prose and verse. The tantras usually have an opening scene describing the setting and the general assembly surrounding the principal deity. Then, there follow individual sections or chapters that deal with specific topics. There seems to be no apparent logical arrangement within individual texts. Some tantras appear to be composed according to a preconceived structure, but in many instances the material is clearly put together in a somewhat disordered manner with the same topics being treated in different sections of the whole text. The principal tantras deal with a wide range of subjects that provide the essential instructions for the practice of tantric methods of liberation. Some texts deal with specific topics; others serve as branches, subtexts or elaborations of the major tantras. In principle, the totality of esoteric texts is referred to in Sanskrit as tantra (Tib. rgyud), a term which, like sūtra, and having similar literal meaning, came to be employed to distinguish this literary tradition from other Buddhist texts included in the early Tripiṭaka collections or among the Mahāyāna sūtras. However, in reality the matter is more complex. The tantric texts bear a number of qualifying terms in their titles. Different texts are named variously as Tantra, "Great Tantra" (mahātantra, rgyud chen po), "Root Tantra" (mūlatantra, rtsa ba'i rgyud), "Tantra King" (tantrarāja, rgyud kyi rgyal po), or again as "Ordinance" (kalpa, rtog pa), "Discourse" (sūtra, mdo),4 "Magical Formula" (dhāranī, gzungs), and "Heroine of Magical Power" (vidyārājñi, rig pa'i rgyal mo).5 These are the most frequently employed terms, but there are several others that are also used in the titles of tantric works. Some of these terms were in existence for a long time before the efflorescence of esoteric literature proper in the eighth and ninth centuries.[page 97]

The whole Tantra section as such, depending on the particular bKa' 'gyur edition referred to, is named simply "Tantra" (rGyud) or "Tantra Collection" (rGyud 'bum). However, it is often divided into two major groups called the "Tantra Collection" (rGyud 'bum) and the "Formula Collection" (gZungs 'dus).6 Whenever a particular bKa' 'gyur contains only one Tantra section, this single section includes all categories of tantric texts. When it is divided into the two "Collections" noted, the "Tantra Collection" comprises all tantric texts that belong to the four classes of Tantra (see below), those Mahāyāna sūtras that are recognized as tantric, magical formulas and all the remaining categories included in the Tantra section of the bKa' 'gyur editions that are not subdivided. The "Formula Collection" comprises over two hundred dhāraṇīs and similar texts, including some sūtras, that were gathered together because of their particular importance for ritual. The majority of texts included in this collection are also found among the texts in the "Tantra Collection."

The tantric texts contained in the bKa' 'gyur are arranged in a certain (sequential) order which seems to be quite deliberate, but difficult to ascertain with accuracy. However, on the whole the arrangement of individual texts follows the classification of tantric texts into the four classes. Thus, the Tantra section begins with works belonging to the Highest Yoga, followed by those of the Yoga, and finally those of the Action and Performance classes. There also exist further stratifications of works that appertain to a particular group of texts within each Tantra class, but the actual arrangement and sequence of tantric texts are not consistently the same in all editions of the bKa' 'gyur. Furthermore, in some bKa' 'gyur collections, the tantras are arranged at the beginning, as the first collection, because they are considered more important than other canonical works, such as the Vinaya or Sūtra collections. In some bKa' 'gyur collections they are placed at the end, as the last collection, which is more in accordance with the historical formation of Buddhist texts.

It is possible to discuss tantric literature without making any particular reference to the bKa' 'gyur. However, since so much effort has been invested by the Tibetan savants in the classification and arrangement of tantric literature in some meaningful manner, it is of importance to the understanding of the complexity and variety of tantric works to be aware of the bKa' 'gyur as the largest repository of such texts.[page 98]

The tantric texts included in the bKa' 'gyur represent translations predominantly from the Sanskrit but also from the Prakrit, Apabhraṃśa and other Indian languages. A certain number of such texts were translated into Tibetan during the first propagation (seventh-ninth centuries C.E.) of Buddhism in Tibet, and the majority during the second propagation (tenth century C.E. onward).7 The translation work was done by a number of well-trained Tibetan experts assisted by Indian masters such as Gayādhara, Advayavajra, Jayasena and others. Among the Tibetan translators Rin chen bzang po became the most renowned. But there were many other competent people such as Śākya ye shes or 'Gos lhas btsas who are also ranked very high.