This monograph discusses Portuguese eugenics within a strong international historiographical comparative framework and situates it within different regional, scientific and ideological types of eugenics in the same period. The author argues about three factors that curtailed the development of eugenics in Portugal: the low level of institutionalization, Catholic opposition and the conservative nature of the Salazar regime. The eugenic science and movement was confined to three principal expressions: individualized studies on mental health, often from a 'biotypological' perspective; a particular stance on racial miscegenation within the context of the existence of large colonies under Portuguese rule; and a diffuse model of social hygiene, maternity care and puericulture. This book not only brings to light an unstudied eugenics movement; it also invites the reader to re-think the relations between northern and southern forms of eugenics, the role of religion, the dynamic nature of eugenics in finding a home for its theories and the nature of colonialism.