This book describes the view of Taoist masters, coming from time immemorial, on sex as a subtle art and a method of spiritual improvement. Here are translations of several ancient treatises on the art of sex by such masters as Zhang Sanfeng (founder of Taijiquan), Lu Dongbin (the great Taoist alchemist), Sun Sy-miao (an outstanding physician of the Tang dynasty) and others. The author himself, who lived for more than 10 years in the mountain Taoist monasteries of the Celestial Empire, where he studied internal practices and wrote books, comments in some detail on these ancient texts in simple language explains what the “art of interior chambers” is, what its basic principles and methods are.