本文從歷史流程的角度入手，眺望密教所展開的情形，藉此窺知密教對南亞、東南亞、東北亞、中國及西藏等地的文化造成的影響。這裡分成五章：壹、序言；貳、密教思想發生的社會基礎；參、南印度地方的政治社會情況與密教的確立；肆、波羅王朝與金剛乘的出現；伍、末期的密教與伊斯蘭教徒的入侵。由於密教未能有正確地報導，以致造成扭曲或誤解，實為遺憾之事。今草就此文，視為密教簡史，可也。此中，十一世紀的蘇門答臘島為南海佛國密教最興隆之地，金洲法稱大師的著作由阿底峽（982-1054）在1042年帶入藏區阿里，譯成藏文收入在西藏大藏經內，此事蹟讓筆者驚嘆不已！印尼與西藏在十一世紀因佛緣而締結了手足之情誼。最後，西藏佛教最注重戒律，由總結印度佛教的《時輪金剛經》得到證明，且西藏的出家僧侶是持說一切有部的比丘戒（253條戒），又有誰能說他不是出家人呢？

The origin and development of Tantric Buddhism in India has not yet been adequately reported and seldom attracts attention. Dr. B. Bhattacharyya has stated that Tantra was transmitted in the most secret manner possible through an unbroken chain of gurus and disciples, till it gained currency after about 300 years, that is to say, in the seventh, eighth and ninth centuries of the Christian Era, at a time when Vajrayāna had already made great headway and was almost casting into the shade the original and the purer form of the Buddhist religion. But with reference to Chinese versions, we can point out the archetype of Esoteric Buddhism from the fifth or the sixth century in accordance with the three elements of Mantra, Mandala and Mudrā. I conclude that the dawn of Tantric Buddhism is earlier than the era mentioned above. In this paper, I try to describe the development of Tantric or Esoteric Buddhism in India up to the beginning of the thirteenth century. The paper is divided into five sections. Section 1 is the preface. Section 2 presents the arising of esoteric thought in the social substratum. Section 3 describes the socio-political situation in Southern India and the establishment of Tantric or Esoteric Buddhism. Section 4 focuses on the Pāla Dynasties and the appearance of Vajrayāna Buddhism. Section 5 depicts the final Tantric or Esoteric Buddhism of Southern Asia, Southeast Asia, and East Asia, above all in Sumatra and Tibet.