To practising bonpos, Bon simply means the true religion of Tibet, while to Tibetan Buddhists, Bon refers to the false teachings and practices that were prevalent before Buddhism finally succeeded in gaining a firm hold on the country. The present study resulted from a period during which the author, a renowned scholar of Asian languages and cultures, was engaged in intense contact with practicing bonpos. It consists of the translation of fundamental texts of Bon, based on a manuscript of some 400 years of age, in which the entire Bon tantric practice is summarized. In many ways remarkably parallel to the early Buddhist teachings, much of the Bon tradition was subsequently incorporated back into Buddhism when that religion was formally adopted into Tibetan culture. This important study, first published in the 1960s and long out of print, will be welcomed by all with interest in the religions of the Himalayas.