This article presents a brief discussion of the key questions which were in the focus of interest in research on bilingualism in the last five decades, particularly in the field of bilingual language acquisition. We highlight how the initially negative view of bilingualism has changed based on scientific evidence. The overview starts with a discussion of some of the paths already taken in research on bilingualism, with a focus on the major findings concerning bilingual language development and the consequences of these findings for current views of bilingualism. The discussion moves, then, to the current research questions in this field, discussing the different methodologies used, as well as specific advances in the area of clinical linguistics. We conclude with a discussion on the topics that we believe still need further investigation, namely the nature of the interactions between the language systems of bilingual speakers and the role of the age of onset of bilingualism.