This article places a reconsideration of the Spanish anarchist doctor Félix Martí Ibáñez's work on sexual morality and, in particular, homosexuality within the dual historiographical framework of scientific ideas and anarchism's own history of engagement with these subjects. It argues that recent developments in the writing of the history of anarchism have paid far more attention to the articulation of cultural issues within anarchist movements as part of their overall contestation against the 'bourgeois', religious and capitalist world and sets this article within this renewed framework. The thought of Félix Martí Ibáñez is assessed not for its supposed 'scientificity' but for what it tells us about the eclectic nature of Spanish anarchism at the time and for what such thought signifies for today's libertarian movement.