Visions of Filth explores how notions of deviancy and social control are dramatised in the novels of the late-nineteenth-century Spanish realist author Benito Perez Galdos. A link is made between deviancy and 'filth', a concept arising from the images of dirt, disease, immorality and disorder generated by social abnormality. Galdos's treatment of those groups of the population perceived as 'deviant', in particular prostitutes, alcoholics, beggars and vagrants, is studied within the context of the socio-cultural and medical debates circulating during the period. The issue of deviancy is also examined in relation to gender, by looking at the different attitudes adopted by both Galdos and by social and moral commentators of the time towards certain kinds of male and female deviancy. Drawing on Foucault's very specific conceptualisation of the idea of control through discourses, the book analyses how Galdos's novels interacted with contemporary debates on poverty and deviancy - notably, discourses on hygiene, domesticity and philanthropy. It is proposed that Galdos's view of marginal social groups was much more open-minded, shrewd and liberal than the often inflexible pronouncements made by contemporary professional voices. The establishment of a socio-historical and theoretical framework enables the reader to appreciate the significance of Galdos's critical focus and personal contribution to such discourses.