Current research on bilingualism and multilingualism raises a number of questions central to linguistic enquiry. What does multilingualism tell us about linguistic structure and about the physiological dimensions of the human capacity for language? Why do people use more than one language? How do people become multilingual? This essay will outline some of the major work in each of these areas of enquiry beginning with the studies which are the clearest foundations of the current construction of the field, in terms of the delineation of interest in cognitive, social psychological, sociolinguistic and sociological or anthropological dimensions of multilingualism. Examinations of the cognitive dimensions of multilingualism, centered in neurolinguistic and psycholinguistic approaches, have focused on issues of language processing and language acquisition. Social psychological studies have explored language attitudes and psychological motivations for multilingual language practices. Sociolinguistic analysis has addressed the systematicity of multilingualism, linking multilingual practices in social interaction to cognitive constructions of the world and to language learning processes. Sociological and anthropological approaches used the study of multilingualism to understand important social processes, such as the definition and establishment of personal and political power, and social inequality. The final section of this essy will focus on ways in which studies of multilingualism have facilitated linkages between cognitive, interactional-pragmatic, sociolinguistic and sociological or anthropological areas of concern and outline some opportunities that an integrated approach may present, not only for the development of theory but also for public policy and practice.