1This enlightening work investigates the history, incidence, and causes of a unique sexual lifestyle pursued by increasing numbers of couples. It is called by many names, and lived in a variety of ways by different couples. The most common terms used to describe it are 'hotwife' or 'cuckold lifestyle.' This sexual practice, a form of sexual nonmonogamy, is distinguished from swinging and polyamory in that the husband rarely seeks sexual contact outside the marriage except for participation in group sex with his wife and other men, while the wife is permitted and often encouraged to pursue unrestrained sexual encounters with other men. The author includes interviews and comments from couples living the lifestyle throughout the U.S., and presents the stories in an attempt to determine the history of this sexual practice and its role in society and in relationships. He explores the psychological, social, biological, and evolutionary underpinnings of this uncommon and socially taboo behavior in an effort to make it more comprehensible to those engaged in the lifestyle and those who are just curious.