The objective of this book is to bring to the earnest readers the unique significance and the deep philosophy behind the Gayathri Mantra and the Sandhya Upasana. The author of this book, Swami Mukhyananda, has dealt with these in depth, giving the philosophic significance of their practices and their pragmatic value. And for the benefit of those who want to perform Sandhya systematically, the complete details regarding the mantras to be chanted and procedures to be adopted are given in this book. The mantras are given in Devanagari script with transliteration and English translation.