Hevajra (Tib. Kye'i rdo rje) is one the principal i'adevat? (Tib. Yidam) or meditational deities of tantric Buddhism and is key to Sa skya pa practice in Tibetan Buddhism. Professor SWnellgrove's edition of the Hevajra-tantra has been prepared on the basis of the extant Sanskrit manuscripts, the core being a Sanskrit original found in Nepal in the 19th century. The translation is made with reference also to the Tibetan edition of the tantra, as well as the most important Indian commentaries, among which is the Yogaratnam'l? by K'ha, here reproduced in full. The first part is in two sections: the introduction provides historical & religious setting, and then interprets the essential meaning of the tantra; then follows the complete translation, with full explanatory notes based upon the commentaries. The second part contains the complete romanised Sanskrit and Tibetan texts of the tantra, followed by Yogaratnam'l'. Both versions of the text are fully annotated, and followed by a select vocabulary: Tibetan-Sanskrit-English, then Sanskrit-Tibetan.