Sexual compatibility between male and female partners is in­ dispensable to normal and successful fertilization in mammals. Thus, the genes from males and females whose sexual behavior is characterized by awkwardness, ineptness, and miscues are elimi­ nated from the gene pool of the species. In human societies, this compatibility is not always evident; and the behavior that precedes and accompanies copulation and fertilization is exceed­ ingly complex and affected by many variables. As in most other species of animals, the entire repertoire of reproductive behavior of man is not well understood by man. When viewed, discussed, or reported, the topic is too often and most unfortunately regarded as an amalgam of emotion, mysticism, and biology. In the past, such emotion-charged approaches to the biologi­ cal fact of reproduction did much to obfuscate the subject; and as a result, much of the array of hormonal, neural, psychological, and social variables that control and insure the successful repro­ duction of the human species remains even now in Victorian ignor­ ance. But with the recent rash of books and scientific treatises on the subject, some progress has been made in elucidating human reproduction and associated sexual behavior. However, so entrench­ ed are some of our social taboos that the danger still lurks of equating social acceptance of the words with an understandin- all too lacking—of the process to which they refer.