The issues raised by eugenics are of more than passing interest for the student of political thought. In itself a minor offshoot of turn-of-the-century socio-biological thought which never achieved ideological ‘take-off’ in terms of influence or circulation, there was certainly more in eugenics than nowadays meets the eye. The following pages propose to depart from the over-simplistic identification of eugenics, as political theory, with racism or ultra-conservatism and to offer instead two alternative modes of interpretation. On the one hand, eugenics will be portrayed as an exploratory avenue of the social-reformist tendencies of early-twentieth-century British political thought. On the other, it will serve as a case-study illustrating the complexity and overlapping which characterize most modern ideologies. While recognizing, of course, the appeal of eugenics for the ‘right’, a central question pervading the forthcoming analysis will be the attraction it had for progressives of liberal and socialist persuasions, with the ultimate aim of discovering the fundamental affinities the ‘left’ had, and may still have, with this type of thinking.