Anal manipulation and penetration produce stimulation enjoyed as sexual by some people. Although this type of sexual activity is not new, the current social climate of sexual freedom and experimentation has brought it out into the open. This paper reviews some of the anatomical, physiological, and behavioral aspects of this variation of human sexual gratification, and provides the practicing professional, who has to deal with questions on anal sexuality, with information on the subject and suitable background material and literature references for further study.