The interest of the psychologist in bilingualism from its origins in the early 1900's to the present is traced. Bilingualism and intelligence are discussed as well as some recent studies on bilingualism and cognitive development. Several areas where psychologists may provide valuable insights into the process of becoming bilingual are discussed with their educational applications. It is suggested that studies of the relationship between intelligence and bilingualism have been unhelpful because: they lacked proper controls; standardized tests almost always discriminate against those (e.g., most ethnic groups) who were not part of the standardization sample; and such tests allow little direct access to the nature of cognitive processing involved. Many of the studies on bilingualism and cognitive development have sought to demonstrate that there are no cognitive "deficits" resulting from bilingualism, and most recent studies seem to wish to demonstrate that "bilingual is better." Some investigators are interested in the theoretical basis of cognition and have found bilingual subjects an interesting group to study. Studies have also been motivated by the belief that the practical issues of bilingual education, such as language learning and literacy, may be based in important ways on cognitive skills. Two areas of research that remain practicable and interesting are within-population experimental designs relating linguistic proficiency to cognitive skills, and the study of reading acquisition in first and second languages. (SW)