Since classical times there has been discussion on the existence or non-existence of variations in libido in women during the menstrual cycle.*This discussion reached its peak in the nineteenth and early part of the present century.The main difference of opinion lay between those who believed that there was increased libido in association with menstruation itself-that is, just before, just after, or during, or various combinations thereof (for example, Campbell, 1891 ; Kossmann, 1903; Havelock Ellis, 1910)-and those who denied the existence of any monthly enhancement of sexual desire in women (for example, Ftirbringer, 1918).The more recent literature continues to show marked differences of opinion.Thus Corner (1952) maintained that libido is maximal just before or just after menstrua- tion, whereas Stopes (1937) considered the monthly rhythm to have two peaks, one just before menstruation and the other at mid-cycle.On the other hand, Eckstein and Zuckerman (1956) stated that " sexual behaviour in women very rarely manifests any rhythmic pattern."However, according to Swyer (1954), " Psychic changes occur throughout the menstrual cycle.So great are the variations in different individuals that generalizations are difficult to draw.Thus, whereas some women lose all or most of their libido during the menstrual period,