The contents of this book focus on the evolution and practice of mantra. This work consists of five chapters. The second and third chapters discuss the historical speculation of mantra and the purpose of mantric practice and its practical aspect in Brahmanic and Buddhist traditions respectively. The fourth chapter draws out the basic theory of mantric practice, and clarifies the role of mantra in Esoteric Buddhism. Firstly, it brings out the theory of vibration and symbolism in the practice of mantra, and from them it examiners how they are applied to mantic practice. The book highlights the position of mantra in Esoteric Buddhism. Thus, the definition of Esoteric Buddhism is examined, and the basic theory and practical system of Esoteric Buddhism. Lastly, the dimensions of mantric practice are suggested briefly.