Although O Cortiço by Aluísio Azevedo has been widely commented on since its first publication in 1890, surprisingly issues of racial politics have generally been neglected by literary critics. In this article I read the novel as a reaction against the Positivist “whitening” ideologies. Emerging from the particular historical context of nineteenth century Brazil, in which discussions on modernization through European immigration were largely shaped through the legacy of slavery, O Cortiço decries the absence of institutions that are able to educate these new citizens. For Azevedo, a tireless abolitionist, Brazil will never become a modern country unless it addresses its heritage of slavery. The life stories of the immigrants in the novel, their sexual relationships, offspring and failures, are therefore directly linked to Brazil’s future and the so desired but always elusive modernity.