The book looks at world-wide evidence on three issues that concern all those interested in bilingualism and bilingual education. The first issue is whether speaking two languages affects thinking skills. This is examined in terms of the relationship between bilingualism and intelligence, and also in terms of a wide variety of international research on bilingualism and cognitive development. A critical examination of the research on this first issue highlights the many weaknesses and limitations of such research. However, with expressed reservations, the evidence indicates that bilingualism has positive consequences for thinking skills and cognitive development. The second issue examined is whether children suffer or benefit from education which uses two languages. Traditions, recent developments and research on bilingual education from the USA, Canada, Wales, Ireland, England and Scotland are portrayed and discussed. The conditions of success for bilingual education, the relative merits of different types of bilingual schooling and a critical evaluation of the North American, British and Irish research are each considered. The third issue of the book concerns the role of attitude and motivation in bilingualism. An individual's attitudes and motivation to becoming and remaining bilingual, or to allowing bilingualism to decline, is shown to be crucial. Discussion of this third issue suggests key psychological factors in the status and destiny of languages. The book concludes by integrating the three issues. A wide variety of theories of bilingual development at a personal, social and education level are explored. This provides the basis for a summary of the present state of our understanding about bilingualism and bilingual education.