The purpose of this paper is to demonstrate that Yeats's involvement with the Steinach Operation which Norman Haire performed on him in April 1934 places him on the fringes of the world of eugenics.  The paper first refers to sexologist Norman Haire. The field of sexology whose interest lay in achieving a scientific understanding of sex was founded in the early years of the twentieth century and quickly developed into an academic endeavor. Haire, aiming at the health and happiness of society, threw himself vigorously into the movement of sex education and birth control and was also attracted by the possibi-lities of rejuvenation.  Secondly, the paper examines Yeats's experience with the Steinach Operation. Steinach was a celebrated professor of biology at the University of Vienna. After having investigated the physiology of the gonads, he came to the ultimate conclusion that hormonal action of the gonads was the crucial factor in determining sexual function. Addi-tional experiments led him to deduce that the ligation of the vas deferens would have a rejuvenating effect. It is important to bear in mind that the Steinach Operation was simply a vasectomy resulting in sterilization.  Thirdly, particular attention is paid to Yeats's implication in eugenics. Yeats joined the Eugenics Society in November 1936 probably through the influence of Haire but soon resigned from the Society. Raymond Cattell who took an extreme view of hereditary inheritance and approved of sterilization made a significant contribution to Yeats's thought at this time. It would be no wonder that Yeats looked "distinct-ly out of place" (Bradshaw) in the Society advocating environment-oriented eugenics.  Finally, the paper concludes that Yeats's involvement with the Steinach Operation in 1934, the year of the enforcement of the Nazi Sterilization Law, sets him within the broader context of the British eugenics movement and thus has darker undertones.