It is often said that bilinguals are not two monolinguals in one person. But what does this really mean, especially in the context of bilingual acquisition? The study on which this book is based is the first longitudinal group study of lexical development of French-English bilingual children. The study aims to investigate the nature of the developing bilingual lexicon and its impact on the development of syntax. The key questions addressed include: are bilingual children developing in the same way and at the same rate as their monolingual peers; are there cross-linguistic influences on bilingual acquisition; are there features, patterns or processes specific to bilingual acquisition? The study reports findings from a longitudinal group study of 13 children between 1 and 3 years old who are acquiring French and English simultaneously within the one person – one language framework.