The present article provides an overview of the historical and sociolinguistic factors that have lead to the current state of bilingualism in Catalonia. Since medieval times, offcial policies and successive waves of Spanish-speaking newcomers have left their mark on both the social identity and the linguistic repertoire of the Catalan speech community. At present, surveys show that, despite the legislative efforts of the past 30 years to normalize Catalan as the language of education, culture, and the public sphere in general, the use of Spanish does not appear to be decreasing; rather, overall, there are increasing numbers of bilingual speakers. This, in turn, is having an effect on the variety of Spanish spoken in Catalonia, which shows certain idiosyncratic features, ranging from lexical and grammatical interference to code-switching and code alternation.